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Comprehensive Literature Review: A Guide

What is a literature review, components of a literature review, literature review structures, sample literature reviews, additional resources.

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A literature review is a collection of selected articles, books and other sources about a specific subject. The purpose is to summarize the existing research that has been done on the subject in order to put your research in context and to highlight what your research will add to the existing body of knowledge. Literature reviews are typically organized chronologically, thematically, or based on their methods.

Despite their various structures (see the descriptions below),  literature reviews consist of the following elements :

  • Citations for the referenced materials
  • A discussion of the materials' research purpose, methods, and findings
  • A discussion of how those findings relate to your research
  • A discussion of the similarities and differences between cited materials 
  • A discussion of the gaps created by the material referenced and how your research can close those gaps
  • Chronological
  • Methodological

Chronological order creates paragraph/sections that review the material in sequential order . This structure is useful when tracing the history of a research area. Remember, your materials should be discussed in chronological order regardless of your overarching review structure.

Literature Reviews that are organized methodologically consist of paragraphs/sections that are based on the methods used in the literature found . This approach is most appropriate when you are using new methods on a research question that has already been explored . Since literature review structures are not mutually exclusive, you can organize the use of these methods in chronological order .

Thematic literature review structure organizes paragraphs/sections of the review based on the themes in the literature . This approach may be useful when you are studying a new research problem but would like to contextualize your research with similar literature .

  • Sample Literature Review - Political Science A brief literature review within a political scientists’ National Science Foundation Graduate Research Fellowship grant. Annotated by the University of Wisconsin Madison Writing Center.
  • Sample Literature Review - Philosophy A several-page literature review at the beginning of a published, academic article about philosophy. Annotated by the University of Wisconsin Madison Writing Center.
  • Sample Literature Review - Chemistry A brief literature review at the beginning of a published, academic article about photochemistry. Annotated by the University of Wisconsin Madison Writing Center.
  • Sample Literature Review - Librarianship Extract of literature review from article on collaboration between university libraries and writing centers. Click here for article in full.

These resources provide an overview of the literature review: the purpose of a lit review, what to include in one and how to organize one.

  • University of North Carolina-Chapel Hill Writing Center A thorough description of literature reviews, their purpose, and how to go about writing one.
  • Learn how to write a review of literature (UW-Madison) Outlines the key components of a literature review.
  • University of California-Santa Cruz Library Outlines how to write a literature review. Includes citations for examples of published literature reviews.
  • Literature Reviews: An Overview for Graduate Students What is a literature review? What purpose does it serve in research? What should you expect when writing one?
  • Purdue Owl (Purdue University Online Writing Lab): Writing a Literature Review Breaks down parts and types of literature reviews along with strategies and tips.

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  • Last Updated: Nov 1, 2023 1:03 PM
  • URL: https://libguides.tulane.edu/litreview

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  • UConn Library
  • Literature Review: The What, Why and How-to Guide
  • Introduction

Literature Review: The What, Why and How-to Guide — Introduction

  • Getting Started
  • How to Pick a Topic
  • Strategies to Find Sources
  • Evaluating Sources & Lit. Reviews
  • Tips for Writing Literature Reviews
  • Writing Literature Review: Useful Sites
  • Citation Resources
  • Other Academic Writings

What are Literature Reviews?

So, what is a literature review? "A literature review is an account of what has been published on a topic by accredited scholars and researchers. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available, or a set of summaries." Taylor, D.  The literature review: A few tips on conducting it . University of Toronto Health Sciences Writing Centre.

Goals of Literature Reviews

What are the goals of creating a Literature Review?  A literature could be written to accomplish different aims:

  • To develop a theory or evaluate an existing theory
  • To summarize the historical or existing state of a research topic
  • Identify a problem in a field of research 

Baumeister, R. F., & Leary, M. R. (1997). Writing narrative literature reviews .  Review of General Psychology , 1 (3), 311-320.

What kinds of sources require a Literature Review?

  • A research paper assigned in a course
  • A thesis or dissertation
  • A grant proposal
  • An article intended for publication in a journal

All these instances require you to collect what has been written about your research topic so that you can demonstrate how your own research sheds new light on the topic.

Types of Literature Reviews

What kinds of literature reviews are written?

Narrative review: The purpose of this type of review is to describe the current state of the research on a specific topic/research and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weakness, and gaps are identified. The review ends with a conclusion section which summarizes the findings regarding the state of the research of the specific study, the gaps identify and if applicable, explains how the author's research will address gaps identify in the review and expand the knowledge on the topic reviewed.

  • Example : Predictors and Outcomes of U.S. Quality Maternity Leave: A Review and Conceptual Framework:  10.1177/08948453211037398  

Systematic review : "The authors of a systematic review use a specific procedure to search the research literature, select the studies to include in their review, and critically evaluate the studies they find." (p. 139). Nelson, L. K. (2013). Research in Communication Sciences and Disorders . Plural Publishing.

  • Example : The effect of leave policies on increasing fertility: a systematic review:  10.1057/s41599-022-01270-w

Meta-analysis : "Meta-analysis is a method of reviewing research findings in a quantitative fashion by transforming the data from individual studies into what is called an effect size and then pooling and analyzing this information. The basic goal in meta-analysis is to explain why different outcomes have occurred in different studies." (p. 197). Roberts, M. C., & Ilardi, S. S. (2003). Handbook of Research Methods in Clinical Psychology . Blackwell Publishing.

  • Example : Employment Instability and Fertility in Europe: A Meta-Analysis:  10.1215/00703370-9164737

Meta-synthesis : "Qualitative meta-synthesis is a type of qualitative study that uses as data the findings from other qualitative studies linked by the same or related topic." (p.312). Zimmer, L. (2006). Qualitative meta-synthesis: A question of dialoguing with texts .  Journal of Advanced Nursing , 53 (3), 311-318.

  • Example : Women’s perspectives on career successes and barriers: A qualitative meta-synthesis:  10.1177/05390184221113735

Literature Reviews in the Health Sciences

  • UConn Health subject guide on systematic reviews Explanation of the different review types used in health sciences literature as well as tools to help you find the right review type
  • << Previous: Getting Started
  • Next: How to Pick a Topic >>
  • Last Updated: Sep 21, 2022 2:16 PM
  • URL: https://guides.lib.uconn.edu/literaturereview

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Literature reviews

Writing a literature review.

The following guide has been created for you by the  Student Learning Advisory Service . For more detailed guidance and to speak to one of our advisers, please book an  appointment  or join one of our  workshops . Alternatively, have a look at our  SkillBuilder  skills videos.   

Preparing a literature review involves:

  • Searching for reliable, accurate and up-to-date material on a topic or subject
  • Reading and summarising the key points from this literature
  • Synthesising these key ideas, theories and concepts into a summary of what is known
  • Discussing and evaluating these ideas, theories and concepts
  • Identifying particular areas of debate or controversy
  • Preparing the ground for the application of these ideas to new research

Finding and choosing material

Ensure you are clear on what you are looking for. ask yourself:.

  • What is the specific question, topic or focus of my assignment?
  • What kind of material do I need (e.g. theory, policy, empirical data)?
  • What type of literature is available (e.g. journals, books, government documents)?

What kind of literature is particularly authoritative in this academic discipline (e.g. psychology, sociology, pharmacy)?

How much do you need?

This will depend on the length of the dissertation, the nature of the subject, and the level of study (undergraduate, Masters, PhD). As a very rough rule of thumb – you may choose 8-10 significant pieces (books and/or articles) for an 8,000 word dissertation, up to 20 major pieces of work for 12-15,000 words, and so on. Bear in mind that if your dissertation is based mainly around an interaction with existing scholarship you will need a longer literature review than if it is there as a prelude to new empirical research. Use your judgement or ask your supervisor for guidance.

Where to find suitable material

Your literature review should include a balance between substantial academic books, journal articles and other scholarly publications. All these sources should be as up-to-date as possible, with the exception of ‘classic texts’ such as major works written by leading scholars setting out formative ideas and theories central to your subject. There are several ways to locate suitable material:

Module bibliography: for undergraduate dissertations, look first at the bibliography provided with the module documentation. Choose one or two likely looking books or articles and then scan through the bibliographies provided by these authors. Skim read some of this material looking for clues: can you use these leads to identify key theories and authors or track down other appropriate material?

Library catalogue search engine: enter a few key words to capture a range of items, but avoid over-generalisations; if you type in something as broad as ‘social theory’ you are likely to get several thousand results. Be more specific: for example, ‘Heidegger, existentialism’. Ideally, you should narrow the field to obtain just a few dozen results. Skim through these quickly to identity texts which are most likely to contribute to your study.

Library bookshelves: browse the library shelves in the relevant subject area and examine the books that catch your eye. Check the contents and index pages, or skim through the introductions (or abstracts, in the case of journal articles) to see if they contain relevant material, and replace them if not. Don’t be afraid to ask one of the subject librarians for further help. Your supervisor may also be able to point you in the direction of some of the important literature , but remember this is your literature search, not theirs.

Online: for recent journal articles you will almost certainly need to use one of the online search engines. These can be found on the ‘Indexing Services’ button on the Templeman Library website. Kent students based at Medway still need to use the Templeman pages to access online journals, although you can get to these pages through the Drill Hall Library catalogue. Take a look as well at the Subject Guides on both the Templeman and DHL websites.

Check that you have made the right selection by asking:

  • Has my search been wide enough to ensure that I have identified all the relevant material, but narrow enough to exclude irrelevant material?
  • Is there a good enough sample of literature for the level (PhD, Masters, undergraduate) of my dissertation or thesis?
  • Have I considered as many alternative points of view as possible?
  • Will the reader find my literature review relevant and useful?

Assessing the literature

Read the material you have chosen carefully, considering the following:

  • The key point discussed by the author: is this clearly defined
  • What evidence has the author produced to support this central idea?
  • How convincing are the reasons given for the author’s point of view?
  • Could the evidence be interpreted in other ways?
  • What is the author's research method (e.g. qualitative, quantitative, experimental, etc.)?
  • What is the author's theoretical framework (e.g. psychological, developmental, feminist)?
  • What is the relationship assumed by the author between theory and practice?
  • Has the author critically evaluated the other literature in the field?
  • Does the author include literature opposing their point of view?
  • Is the research data based on a reliable method and accurate information?
  • Can you ‘deconstruct’ the argument – identify the gaps or jumps in the logic?
  • What are the strengths and limitations of this study?
  • What does this book or article contribute to the field or topic?
  • What does this book or article contribute to my own topic or thesis?

As you note down the key content of each book or journal article (together with the reference details of each source) record your responses to these questions. You will then be able to summarise each piece of material from two perspectives:     

Content: a brief description of the content of the book or article. Remember, an author will often make just one key point; so, what is the point they are making, and how does it relate to your own research project or assignment?

Critical analysis: an assessment of the relative strengths and weaknesses of the evidence used, and the arguments presented. Has anything conveniently been left out or skated over? Is there a counter-argument, and has the author dealt with this adequately? Can the evidence presented be interpreted another way? Does the author demonstrate any obvious bias which could affect their reliability? Overall, based on the above analysis of the author’s work, how do you evaluate its contribution to the scholarly understanding and knowledge surrounding the topic?    

Structuring the literature review

In a PhD thesis, the literature review typically comprises one chapter (perhaps 8-10,000 words), for a Masters dissertation it may be around 2-3,000 words, and for an undergraduate dissertation it may be no more than 2,000 words. In each case the word count can vary depending on a range of factors and it is always best, if in doubt, to ask your supervisor.

The overall structure of the section or chapter should be like any other: it should have a beginning, middle and end. You will need to guide the reader through the literature review, outlining the strategy you have adopted for selecting the books or articles, presenting the topic theme for the review, then using most of the word limit to analyse the chosen books or articles thoroughly before pulling everything together briefly in the conclusion.

Some people prefer a less linear approach. Instead of simply working through a list of 8-20 items on your book review list, you might want to try a thematic approach, grouping key ideas, facts, concepts or approaches together and then bouncing the ideas off each other. This is a slightly more creative (and interesting) way of producing the review, but a little more risky as it is harder to establish coherence and logical sequencing.

Whichever approach you adopt, make sure everything flows smoothly – that one idea or book leads neatly to the next. Take your reader effortlessly through a sequence of thought that is clear, accurate, precise and interesting. 

Writing up your literature review

As with essays generally, only attempt to write up the literature review when you have completed all the reading and note-taking, and carefully planned its content and structure. Find an appropriate way of introducing the review, then guide the reader through the material clearly and directly, bearing in mind the following:

  • Be selective in the number of points you draw out from each piece of literature; remember that one of your objectives is to demonstrate that you can use your judgement to identify what is central and what is secondary.
  • Summarise and synthesise – use your own words to sum up what you think is important or controversial about the book or article.
  • Never claim more than the evidence will support. Too many dissertations and theses are let down by sweeping generalisations. Be tentative and careful in the way you interpret the evidence.
  • Keep your own voice – you are entitled to your own point of view provided it is based on evidence and clear argument.
  • At the same time, aim to project an objective and tentative tone by using the 3rd person, (for example, ‘this tends to suggest’, ‘it could be argued’ and so on).
  • Even with a literature review you should avoid using too many, or overlong, quotes. Summarise material in your own words as much as possible. Save the quotes for ‘punch-lines’ to drive a particular point home.
  • Revise, revise, revise: refine and edit the draft as much as you can. Check for fluency, structure, evidence, criticality and referencing, and don’t forget the basics of good grammar, punctuation and spelling.

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When and how to update systematic reviews

Systematic reviews are most helpful if they are up‐to‐date. We did a systematic review of strategies and methods describing when and how to update systematic reviews.

To identify, describe and assess strategies and methods addressing: 1) when to update systematic reviews and 2) how to update systematic reviews.

Search methods

We searched MEDLINE (1966 to December 2005), PsycINFO, the Cochrane Methodology Register (Issue 1, 2006), and hand searched the 2005 Cochrane Colloquium proceedings.

Selection criteria

We included methodology reports, updated systematic reviews, commentaries, editorials, or other short reports describing the development, use, or comparison of strategies and methods for determining the need for updating or updating systematic reviews in healthcare.

Data collection and analysis

We abstracted information from each included report using a 15‐item questionnaire. The strategies and methods for updating systematic reviews were assessed and compared descriptively with respect to their usefulness, comprehensiveness, advantages, and disadvantages.

Main results

Four updating strategies, one technique, and two statistical methods were identified. Three strategies addressed steps for updating and one strategy presented a model for assessing the need to update. One technique discussed the use of the "entry date" field in bibliographic searching. Statistical methods were cumulative meta‐analysis and predicting when meta‐analyses are outdated.

Authors' conclusions

Little research has been conducted on when and how to update systematic reviews and the feasibility and efficiency of the identified approaches is uncertain. These shortcomings should be addressed in future research.

Plain language summary

Systematic reviews are most useful when they are regularly updated. It is not clear, however, when updating should be done and which strategies and methods are most cost‐effectiveThis review identified strategies and methods used to update systematic reviews. Fifteen articles that documented 4 strategies and 2 statistical methods for updating systematic reviews were found. The 4 strategies have not been compared to one another so their practical performances are unclear.

A systematic review is a convenient synthesis of evidence for the busy health care practitioner. Systematic reviews are also increasingly gaining acceptance as a starting point in the development of evidence‐based clinical practice guidelines ( Cook 1997a ; Mulrow 1994 ), and to help design primary research and ensure that it is ethically justified ( Cook 1997b ). Governments and other groups are investing heavily in commissioning and using the results of systematic reviews to inform healthcare practice and policy ( Atkins 2005 ) and recent estimates suggest that approximately 2500 new systematic reviews are published annually ( Moher 2007 ).

Systematic reviews are most useful if they are up‐to‐date ( Atkins 2005 ; Eccles 2001 ). As science evolves with the accumulation of new research, health care interventions previously considered to be effective and safe may in future be shown to be ineffective or harmful, or vice‐versa ( Chalmers 1994 ). There may also be subtle changes in interventions over time (e.g., changes in dosing of medications or improved surgical skills), or in the preferred health outcomes ( Shekelle 2001a ). Ignoring these changes could undermine the validity of systematic reviews. Updating systematic reviews can also be useful when delayed publications or grey literature have been identified, in order to reduce the impact of publication bias (or time lag bias) on the results ( Hopewell 2001 ; Ioannidis 2001 ; Montori 2005 ).

The Cochrane Collaboration, the National Institutes of Health and Clinical Evidence update systematic reviews on a regular basis. Other systematic reviews, which account for about 80% of all published reviews ( Moher 2007 ), are not usually updated. Within two years of their publication, only 3% of systematic reviews published in peer‐reviewed journals had been updated compared to 38% of Cochrane reviews ( Jadad 1998 ; Moher 2007 ).

A potential problem related to updating systematic reviews is the lack of a definition of what an update is. We have defined updating as a process aiming to identify new evidence to incorporate into a previously completed systematic review ( Moher 2006 ). Thus, extending a search to new sources or an exhaustive but fruitless search for new evidence would be considered an update whereas corrections or re‐analysis of a previously published review would not be an update.

Updating a systematic review can be as costly and time‐consuming as conducting the original review or developing the original clinical practice guidelines ( Eccles 2001 ; Shekelle 2001a ). Whether it is appropriate to expend resources for updating depends upon many factors such as the rapidity and scope of scientific and technological developments, nature of the health condition, and its public health importance. We performed a systematic review of the strategies and methods for updating to elucidate this topic and to highlight gaps in the evidence.

To systematically review strategies and methods developed or used for updating systematic reviews in health care. We addressed two specific questions:

1. When to update systematic reviews. 2. How to update systematic reviews.

Criteria for considering studies for this review

Types of studies.

We included:

  • Reports (descriptive or empirical) describing the development, use, or comparison of strategies or methods for updating or determining the need for updating systematic reviews in health care;
  • Updated systematic reviews of health care interventions describing strategies or methods for updating; and
  • Commentaries, editorials or other short reports describing or suggesting strategies or methods for updating systematic reviews of health care interventions.

We excluded:

  • Clinical practice guidelines;
  • Health technology assessments;
  • Strategies or associated methods for updating clinical practice guidelines or health technology assessments.

Types of data

Data from published and unpublished articles providing descriptions of updating strategies and methods.

Types of methods

The identified strategies and methods for updating systematic reviews were compared in terms of their applicability, minimum expertise required to implement the strategy or method, and comprehensiveness (e.g. covered clinical, statistical, and other domains).

Types of outcome measures

The following outcomes were examined:

  • General description of a strategy or method for when and how to update;
  • Underlying assumptions of a strategy or method;
  • Advantages of a strategy or method;
  • Disadvantages of a strategy or method;
  • Time and amount of resources needed to strategy or method;
  • Comprehensiveness of a strategy or method.

Search methods for identification of studies

An experienced information specialist conducted all searches. The searches were not restricted by language, publication type, or study design. The following databases were searched: MEDLINE (1966 to December 2005, Ovid Interface), PsycINFO (1955 to June 2005, Ovid Interface), and the Cochrane Methodology Register (Cochrane Library issue 1, 2006, Wiley Interface).

The search strategy for the Cochrane Methodology Register included ((updating and cumulative meta‐analysis) in keywords or (updat* or maintain*) in All Fields) and (systematic review* or cumulative meta‐analysis* or HTA or clinical practice guideline or clinical guideline) in All Fields.

Citation tracking was performed in SCOPUS (1966 to 2006) and Science Citation Index.

We reviewed a cross‐sectional sample of 300 systematic reviews indexed in MEDLINE in November 2004 for the purpose of searching and finding descriptions of updating strategies or methods ( Moher 2007 ). To determine whether or not a systematic review was an update, we used the definition of update described earlier ( Moher 2006 ). For Cochrane reviews, we examined the full text document and the cover page ('What's new,' 'Contribution of authors,' 'Review first published,' 'Date new studies sought but none were found' sections). For non‐Cochrane reviews we examined the full‐text document. The reference lists of potentially relevant reports were also scanned. The proceedings of the 13th Cochrane Colloquium (22‐26 October 2005) were hand searched to identify strategies or methods not yet indexed in the Cochrane Methodology Register. The authors of potentially relevant reports were contacted for further information.

For MEDLINE and PsycINFO search strategies, see Appendix 1 ; Appendix 2 .

Identifying studies

Three authors independently screened the titles and abstracts of all the retrieved records for their relevancy. The initial broad screen excluded obviously irrelevant records. The authors then performed a second stricter screen by examining full‐text reports of the remaining records as well as the updated systematic reviews indexed in MEDLINE (November, 2004) ( Moher 2007 ). Disagreements regarding the eligibility were resolved through consensus. Reasons for exclusion at all levels of screening were documented.

Assessment of methodological quality

Since there is no validated quality assessment tool that can be applied to strategies or methods for updating, the identified strategies and methods were contrasted based on their methodological strengths and limitations (see 'Data extraction').

Data extraction

Two authors independently completed data extraction using a 15‐item data form. Any disagreements or differences in the extracted data were resolved through consensus. The reviewers contacted the authors of included reports for additional information as required. The following items were abstracted: name of author, country (where the research was done), year of publication, type of publication (e.g. full‐text article, abstract, letter, Internet document, unpublished document), and area of health care. Descriptive information on when and how to update, underlying assumptions, comprehensiveness and applicability (i.e. whether the strategy or method that was described is applicable). The strengths and limitations of the strategies and methods were ascertained and abstracted directly from the reports as well as they were determined through consensus‐based judgment by the review authors.

Data analysis

This was a qualitative methodological systematic review and it did not involve statistical data analysis.

Description of studies

Included studies.

Four strategies ( Chalmers 1993 ; Higgins 2005 ; Lutje 2005 ; Weller 1998 ; Table 1 ), two statistical methods ( Barrowman 2003 ; Baum 1981 ; Berkey 1996 ; Ioannidis 1999 ; Ioannidis 2001 ; Lau 1992 ; Lau 1995 ; Mullen 2001 ; Pogue 1997 ; Sutton 2006 ; Table 2 ), describing when and how to update systematic reviews were eligible for the inclusion in this review.

Three of the four strategies described the sequence of various steps needed for updating systematic reviews ( Chalmers 1993 ; Higgins 2005 ; Weller 1998 ) and one strategy reported a model for assessing the need to update systematic reviews ( Lutje 2005 ). One of the four strategies was published in a peer‐reviewed journal ( Chalmers 1993 ), two strategies were Internet documents ( Higgins 2005 ; Weller 1998 ), and one strategy ( Lutje 2005 ) was reported as a conference abstract.

The two statistical methods were cumulative meta‐analysis ( Baum 1981 ; Berkey 1996 ; Ioannidis 1999 ; Ioannidis 2001 ; Lau 1992 ; Lau 1995 ; Mullen 2001 ; Pogue 1997 ) and tests for determining when a meta‐analysis needs to be updated ( Barrowman 2003 ; Sutton 2006 ). All but one report of the two statistical methods ( Barrowman 2003 ; Baum 1981 ; Berkey 1996 ; Ioannidis 1999 ; Ioannidis 2001 ; Lau 1992 ; Lau 1995 ; Mullen 2001 ; Pogue 1997 ) were published in peer‐reviewed journals. One report ( Sutton 2006 ) was a conference abstract (see "Characteristics of Included Studies" table).

Excluded studies

The majority of the excluded records were reports of clinical practice guidelines, updated systematic reviews or meta‐analyses not describing any particular updating method, health technology assessments, or empirical studies assessing the impact of updating on effect estimates of previously conducted meta‐analyses (see "References to excluded studies").

Ongoing studies

We did not find any ongoing studies . The full text publication for one of the included statistical methods in this review is in progress ( Sutton 2006 ).

Risk of bias in included studies

The methodological quality of the identified studies was not formally assessed. The included strategies and methods were descriptively compared based on their strengths and limitations ascertained as described above.

Effect of methods

Results of literature search.

A total of 2550 records (titles and abstracts) were initially screened. Of these, full‐text reports of 223 records were reviewed and 15 articles met the inclusion criteria ( Barrowman 2003 ; Baum 1981 ; Berkey 1996 ; Chalmers 1993 ; Higgins 2005 ; Ioannidis 1999 ; Ioannidis 2001 ; Lau 1992 ; Lau 1995 ; Lutje 2005 ; Mullen 2001 ; Pogue 1997 ; Sutton 2006 ; Weller 1998 ). None of the 54 updated systematic reviews identified from our cross‐sectional sample reported a description of an updating strategy or method. The screening process is summarized in the study flow chart (Figure 01). The fifteen articles included in the review reported four strategies ( Chalmers 1993 ; Higgins 2005 ; Lutje 2005 ; Weller 1998 ; Table 1 ), and two statistical methods ( Barrowman 2003 ; Baum 1981 ; Berkey 1996 ; Ioannidis 1999 ; Ioannidis 2001 ; Lau 1992 ; Lau 1995 ; Mullen 2001 ; Pogue 1997 ; Sutton 2006 ; Table 2 ) describing when or how to update systematic reviews.

The updating strategies were: a) steps in maintaining an updated review ( Chalmers 1993 ; Higgins 2005 ), b) assessment of the need to update ( Lutje 2005 ) and c) strategies for updating a review ( Weller 1998 ; Table 1 ). One of the strategies was published in a peer‐reviewed journal ( Chalmers 1993 ), two strategies were Internet documents ( Higgins 2005 ; Weller 1998 ), and one strategy ( Lutje 2005 ) was reported as conference abstract. The two statistical methods were: a) determining when a meta‐analysis requires updating ( Barrowman 2003 ; Sutton 2006 ) and b) cumulative meta‐analysis ( Baum 1981 ; Berkey 1996 ; Lau 1992 ; Lau 1995 ) (with methodological extensions: using the cumulative slope ( Mullen 2001 ), sequential monitoring boundaries ( Pogue 1997 ), and so‐called 'recursive' cumulative meta‐analysis ( Ioannidis 1999 ; Table 2 ). Both statistical methods were published in peer‐reviewed journals; however, one was a conference abstract ( Sutton 2006 ).

Strategies for updating systematic reviews

Steps in maintaining an updated review.

Recognizing the importance of updating systematic reviews in health care, Chalmers et al. summarized and presented a strategy for maintaining updated systematic reviews of randomized controlled trials evaluating the effect of perinatal care (Chalmers 1993). The updating process for this strategy consists of the identification, retrieval, and incorporation of new information into a database as well as the dissemination of updated systematic reviews. The strategy of maintaining continuously updated systematic reviews is accomplished through the following 7 steps: identifying potentially eligible trials (e.g., MEDLINE search, hand search of core journals, searches of conference abstracts), obtaining copies of eligible reports, entering eligible trials into a central database (e.g., reference citation, study characteristics), distributing topic‐specific work lists to authors (e.g., titles of existing trials), describing tasks to authors (e.g., data abstraction, quality assessment, statistical analysis, contacting trial authors), updating the core database (e.g., amendment of existing reviews, central editorial checking), and preparing data for dissemination (e.g., online publication, books, disks). According to the authors' experience, the adoption of this approach supported by the use of an electronic format has proved to be useful not only in editing the existing publications but also in preparing and disseminating future publications.

Maintaining an updated review

When registering a review with the Cochrane Collaboration, the review authors agree to keep it up‐to‐date ( Higgins 2005 ). The Cochrane Collaboration recommends periodic updating of the literature search (e.g., every two years) to determine whether or not relevant new studies are available for inclusion in a previously completed systematic review. If a review is updated less frequently than every two years, the Collaboration requires that reviewers provide a commentary explaining the reasons why. The electronic‐based format of Cochrane reviews allows for easy, rapid updating or correcting, with the publication of a new issue of the Cochrane Library every three months. An important limitation of the Collaboration's strategy is its arbitrarily pre‐set updating frequency, which may result in an inefficient use of resources in slowly developing fields of health care or delayed incorporation of new knowledge in rapidly evolving fields.

Assessment of the need to update

The Cochrane Infectious Disease Group has proposed an editorial strategy for updating their reviews and an algorithm of administrative actions needed for updating ( Lutje 2005 ). The strategy involves two steps and follows a two‐year cycle updating policy. The first step is to assess whether or not a given systematic review is up‐to‐date by considering the age of the review, availability of new relevant trials, and the number of participants in the new trials. The second step is to assess the importance of the topic through ascertaining the burden of disease and pace of development of the field. The latter is useful for planning topic‐specific priorities in terms of updating. Both steps of the strategy involve judgemental decisions reached by an editorial consensus. This strategy provides information on when and how to update systematic reviews and assists in assigning an order of priority to reviews in need of updating. However, it is not clear how to determine whether a given review is up‐to‐date.

Strategies for updating a review

Weller proposed updating strategies that are designed to guide authors as to when and how to update evidence reported in systematic reviews, health technology assessment reports, and CPGs ( Weller 1998 ). When planning and conducting an update, these strategies suggest considering clinical end‐points (e.g., short‐ vs. long‐term clinical outcomes), treatment characteristics (e.g., state of evolution of the field), statistical methodology (e.g., the conduct of cumulative meta‐analyses), public health impact of treatments, and the availability of resources. This strategy is broadly applicable but lacks the detail needed for practical utility.

Statistical methods for updating systematic review

Predicting when meta‐analyses require updating.

Barrowman et al. proposed a diagnostic test to assess whether a sufficient amount of evidence may have been accrued to turn a statistically non‐significant result of a meta‐analysis into a significant one ( Barrowman 2003 ). Computer simulations indicated that the diagnostic test identified whether or not a meta‐analysis was out of date with a sensitivity between 49% and 62% and a specificity between 80% and 90%, depending upon the configuration of the simulation. This method predicts the appropriate timing for an update, requiring searching, screening, and only partial data extraction (e.g., number of additional participants), rather than spending considerable resources performing a full‐scale update including a comprehensive data extraction for each new trial or with an arbitrarily set frequency. The application of this method is limited to meta‐analyses with 'statistically non‐significant' results under the assumption that this may have been due to insufficient power.

Sutton et al. proposed a similar method to the diagnostic test proposed by Barrowman and colleagues ( Sutton 2006 ). This method assesses the sample size of a trial required to change the findings of a meta‐analysis and can be used to predict whether trials awaiting assessment would change the conclusions of a pre‐existing systematic review. This method can therefore be used by review authors to prioritize which reviews require updating.

This method was presented at the XIV Cochrane Colloquium, Dublin, Ireland in 2006. We've been in contact with the first author and are currently waiting for this method to be published in full).

Cumulative meta‐analysis

This is a statistical procedure in which the combined effect estimate is sequentially updated by incorporating results from each newly available study ( Baum 1981 ; Berkey 1996 ; Lau 1992 ; Lau 1995 ). It documents trends in a treatment effect over time and provides clinicians and policy makers with up‐to‐date information. Cumulative meta‐analysis now a commonly used technique in healthcare research; its methodology has been well described ( Egger 2001 ; Sutton 2002 ). When done prospectively, cumulative meta‐analysis may identify the earliest time at which there is sufficient statistical evidence that an intervention is non‐inferior, efficacious or harmful, thereby serving as a signal to stop trials that are underway earlier than planned (or at least not to initiate any new ones) because of ethical concerns as well as economic implications ( Lau 1995 ).

Although it can be very useful, the application of cumulative meta‐analysis is a costly and cumbersome process. One important limitation of cumulative meta‐analysisis an inflated rate of type‐I error due to repeated hypothesis testing, which necessitates the adjustment of the alpha level of statistical significance (Brok 2005; Chalmers 1991 ; Pogue 1997 ).

Cumulative meta‐analysisusing the cumulative slope as an indicator of stability

Mullen et al. introduced the "cumulative slope" as an indicator of stability of the pooled effect size in cumulative meta‐analysis, arguing that it is a more objective alternative to visual inspection of cumulative meta‐analysis ( Mullen 2001 ). A least‐squares regression line is fitted to N data points corresponding to the effect size of each successive study plotted cumulatively across k waves at which a new study is added. The slope of the regression line fitted over N data points and k waves is the rate of change in Z effect size corresponding to the addition of each new study. The smaller the magnitude of the slope of the regression line is, the greater the confidence that the pooled effect size is becoming stable, suggesting no need for further updating.

The cumulative slope may be used prospectively to discern when it is appropriate to stop updating a SR in order to avoid waste of resources. The retrospective use of the cumulative slope may help to uncover heterogeneity amongst studies, or to expose conduct of possibly unnecessary studies. Important limitations of this method are its subjectivity, repeated use of the same studies, multiple testing, and that it does not yield a valid estimate of variance for the cumulative slope.

Cumulative meta‐analysis using sequential monitoring boundaries

Repeated hypothesis testing as data accumulate leads to an inflated type‐I error. The significance levels of the individual hypothesis tests therefore need to be adjusted so that the cumulative overall error rate does not exceed the pre‐specified level of statistical significance. To address this problem, Pogue and Yusuf proposed the adaptation of sequential monitoring boundaries (e.g., Lan and DeMets alpha‐spending functions) used in clinical trials, to the conduct of cumulative meta‐analyses ( Friedman 1998 ; Pogue 1997 ).

The optimal information size (OIS), a measure of the total amount of information estimated for cumulative meta‐analysis, is similar to the total sample size needed to detect a pre‐specified effect size with a given statistical power calculated for a single planned trial. The OIS calculation involves a priori specification of assumed realistic event rates in the control arm for the disease and outcome of interest, the clinically important minimum treatment effect size, and type‐I and type‐II error rates. Estimation of the OIS and the utilization of monitoring boundaries provide a prospective context in which to examine trends as evidence accumulates, and to evaluate the statistical strength of the evidence of the treatment benefit (or harm) by taking into account the number of patients observed as a proportion of OIS each time an analysis is performed, while adjusting for multiple testing. Limitations of using monitoring boundaries and the OIS are that a large amount of data and a priori specification of various parameters are required.

Recursive cumulative meta‐analysis

Ioannidis et al. proposed recursive cumulative meta‐analysis as an extension of conventional cumulative meta‐analysis ( Ioannidis 1999 ; Ioannidis 2001 ). Recursive cumulative meta‐analysis allows investigators to explore and document the evolution of the pooled treatment effect of meta‐analysis in successive information steps as new data are incorporated into the results. The pooled effect estimate is recalculated at each information step. When recursive cumulative meta‐analysis is restricted to recalculating the pooled treatment effect only when a new study is published without incorporating updated, corrected, more accurate, or unpublished data, it is no different from a traditional cumulative meta‐analysis ( Ioannidis 1999 ). Recursive cumulative meta‐analysis is useful for evaluating and comparing the impact of updating, publication bias, and publication lag on the pooled treatment effect estimates in meta‐analyses of individual patient data versus summary data. However, unpublished and updated data for detailed analyses need careful scrutiny for accuracy and completeness in order to avoid bias, rendering the conduct of recursive cumulative meta‐analysis cumbersome and costly.

We identified four strategies describing when or how to update systematic reviews, but, mostly, they do not include quantitative techniques ( Chalmers 1993 ; Higgins 2005 ; Lutje 2005 ; Weller 1998 ), are arbitrary in nature ( Higgins 2005 ; Lutje 2005 ), may be inefficient ( Chalmers 1993 ; Higgins 2005 ; Weller 1998 ), are limited in their practical applicability ( Higgins 2005 ; Weller 1998 ), or are not sufficiently comprehensive (i.e., covering only one or two domains ‐ search strategy or administrative steps) ( Chalmers 1993 ; Higgins 2005 ; Lutje 2005 ; Weller 1998 ). The practical performance of these approaches is unclear because they have not been empirically tested or compared to one another.

Conventional cumulative meta‐analysis and its methodological extensions ( Baum 1981 ; Berkey 1996 ; Ioannidis 1999 ; Ioannidis 2001 ; Lau 1992 ; Lau 1995 ; Mullen 2001 ; Pogue 1997 ) are resource‐consuming approaches for updating. Although the method by Barrowman et al. is less resource‐intensive than CMA, it is strictly a statistical approach that can only be used for meta‐analyses with statistically non‐significant results ( Barrowman 2003 ). It appears that this method, along with Sutton's method ( Sutton 2006 ), have not been widely used.

The relative paucity of well‐elaborated methods for updating systematic reviews contrasts sharply with the substantial developments in other methodological areas relating to the conduct of systematic reviews. For example, a recently completed SR identified more than 30 methods of variance imputation ( Wiebe 2006 ). Likewise, many methods have been proposed to identify and adjust for publication bias ( Song 2000 ; Sutton 1998 ).

Apparently more attention, work and resources have been devoted to the development and empirical evaluation of the methodology for updating CPGs than for systematic reviews ( Clinton 1994 ; Dillon 2005 ; Gartlehner 2004 ; Johnston 2003 ; Shekelle 2001a ; Zarnke 2000 ; Table 3 ). For example, these methods have focused on when and how to update searches to inform the currency of a CPG, the public health importance of a CPG, and efficient and pragmatic ways to update a CPG ( Table 3 ). Their performance in terms of validity and efficiency has also been evaluated ( Gartlehner 2004 ; Johnston 2003 ; Shekelle 2001b ).

One of the reasons for the disparities in scientific attention directed at developing updating methods for CPGs compared to systematic reviews may be that CPGs are produced by organizations committed to updating, whereas many systematic reviews are produced by researchers who may lack the resources or the academic motivation needed for updating.

The findings of our review suggest that, apart from Cochrane reviews, the importance of updating systematic reviews has not been well recognized, and that considerably more investment should be made to investigate the issues. Additional efficiency may be gained with international harmonization of aspects of the updating process, such as the Guidelines International Network initiatives. Electronic formats, similar to the one used by the Cochrane Collaboration, would offer an efficient and convenient way of maintaining, modifying, and disseminating the findings of SR updates ( Chalmers 1986 ).

Moreover, future research should focus on identifying predictors for the need to update systematic reviews. Finally, a survey of national and international organizations that fund or conduct systematic reviews would provide valuable insights into the updating practices or policies of such groups.

We did not search for literature on the economic issues of updating systematic reviews, and did not find any incidentally. The cost‐effectiveness of alternative methods for identifying reviews in need of updating should be explored (e.g. the acceptability of the incremental cost of updating per unit of change in study results). Methods developed in other fields could also be considered for their potential to inform when and how to update systematic reviews. For example, value‐of‐information analysis may identify a benefit for decision‐making of reduced uncertainty, even if the clinical conclusions of the updated review remain unchanged ( Claxton 2004 ).

Although methods for assessing publication bias can be used as a supplementary tool for updating systematic reviews, they were not included in this review and are reviewed elsewhere ( Song 2000 ; Sutton 1998 ). Since the identification of methods for updating CPGs was not the focus of this SR, it is possible that other methods exist beyond the ones we identified.

In summary, very few strategies or methods exist for updating systematic reviews and the identified strategies are not pragmatic and have not been empirically tested. More concerted research efforts are needed to bridge these knowledge gaps and to evaluate the benefits of developing internationally harmonized, efficient, and valid ways of updating systematic reviews.

Implication for methodological research

Research is needed to study and compare different strategies and methods for updating systematic reviews. International harmonization of updating methodology and related activities in the field of systematic reviews is another important issue, which needs to be considered for future research.

Protocol first published: Issue 3, 2005 Review first published: Issue 1, 2008

Acknowledgements

We would like to thank Mr. Raymond Daniel for his assistance in article location and retrieval and Dr. Peter Gøtzsche for guiding us through the editorial process.

Appendix 1. MEDLINE search strategy

The search terms for MEDLINE were:

1. Meta‐Analysis/ 2. Practice Guidelines/ 3. Technology Assessment, Biomedical/ 4. exp "Review Literature"/ 5. (systematic review$ or cumulative meta‐analys$ or hta or ((clinical or prevent$) adj2 guideline$)).mp. 6. or/1‐5 7. ((updat$ or maintain$) adj5 (systematic review$ or cumulative meta‐analys$ or hta or ((clinical or prevent$) adj2 guideline$))).mp. 8. Time Factors/ 9. 6 and 8 10. An update.ti. 11. (update$ and maintain$).ab. 12. updat$.ti. and (updat$ or maintain$).ab. 13. updat$.ab. /freq=2 14. updating.ti. 15. or/11‐14 16. 15 not 10 17. 16 and (or/1‐4) 18. "value of information".mp. 19. or/7,9,17‐18 20. limit 19 to (editorial or letter) 21. limit 19 to meta analysis 22. "systematic review of the literature".ti. 23. or/20‐22 24. 19 not 23

Appendix 2. PsycINFO search strategy

The search terms for PsycINFO were:

1. Meta‐Analysis/ 2. Treatment Guidelines/ 3. "literature review"/ 4. (systematic review$ or cumulative meta‐analys$ or hta or ((clinical or prevent$) adj2 guideline$)).mp. 5. or/1‐4 6. ((updat$ or maintain$) adj5 (systematic review$ or cumulative meta‐analys$ or hta or ((clinical or prevent$) adj2 guideline$))).mp. 7. Time/ 8. 5 and 7 9. An update.ti. 10. (update$ and maintain$).ab. 11. updat$.ti. and (updat$ or maintain$).ab. 12. updat$.ab. /freq=2 13. updating.ti. 14. or/10‐13 15. 14 not 9 16. 15 and (or/1‐3) 17. "value of information".mp. 18. or/6,8,16‐17 19. limit 18 to meta analysis 20. "systematic review of the literature".ti. 21. limit 18 to (5100 journal editorial or 5500 journal letter) 22. or/19‐21 23. 18 not 22 24. limit 23 to yr=1955‐2005

Characteristics of studies

Characteristics of included studies [ordered by study id], characteristics of excluded studies [ordered by study id], contributions of authors.

MS conducted literature searches. DM, AT, ACT, and MS screened the records for inclusion. AT and ACT extracted data from the reports. AT obtained further information from authors and entered the data into RevMan. NJB provided insight into statistical methods. All authors interpreted the results and contributed to editing the manuscript DM, AT, and ACT drafted different parts of the manuscript. ME, JG, MS, and NJB provided comments on the draft.

Sources of support

Internal sources.

  • No sources of support supplied

External sources

  • Canadian Agency for Drugs and Technologies in Health, Canada.

Declarations of interest

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  • What is a Literature Review? | Guide, Template, & Examples

What is a Literature Review? | Guide, Template, & Examples

Published on 22 February 2022 by Shona McCombes . Revised on 7 June 2022.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research.

There are five key steps to writing a literature review:

  • Search for relevant literature
  • Evaluate sources
  • Identify themes, debates and gaps
  • Outline the structure
  • Write your literature review

A good literature review doesn’t just summarise sources – it analyses, synthesises, and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

Why write a literature review, examples of literature reviews, step 1: search for relevant literature, step 2: evaluate and select sources, step 3: identify themes, debates and gaps, step 4: outline your literature review’s structure, step 5: write your literature review, frequently asked questions about literature reviews, introduction.

  • Quick Run-through
  • Step 1 & 2

When you write a dissertation or thesis, you will have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

  • Demonstrate your familiarity with the topic and scholarly context
  • Develop a theoretical framework and methodology for your research
  • Position yourself in relation to other researchers and theorists
  • Show how your dissertation addresses a gap or contributes to a debate

You might also have to write a literature review as a stand-alone assignment. In this case, the purpose is to evaluate the current state of research and demonstrate your knowledge of scholarly debates around a topic.

The content will look slightly different in each case, but the process of conducting a literature review follows the same steps. We’ve written a step-by-step guide that you can follow below.

Literature review guide

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Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

  • Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
  • Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
  • Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
  • Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research objectives and questions .

If you are writing a literature review as a stand-alone assignment, you will have to choose a focus and develop a central question to direct your search. Unlike a dissertation research question, this question has to be answerable without collecting original data. You should be able to answer it based only on a review of existing publications.

Make a list of keywords

Start by creating a list of keywords related to your research topic. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list if you discover new keywords in the process of your literature search.

  • Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
  • Body image, self-perception, self-esteem, mental health
  • Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some databases to search for journals and articles include:

  • Your university’s library catalogue
  • Google Scholar
  • Project Muse (humanities and social sciences)
  • Medline (life sciences and biomedicine)
  • EconLit (economics)
  • Inspec (physics, engineering and computer science)

You can use boolean operators to help narrow down your search:

Read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

To identify the most important publications on your topic, take note of recurring citations. If the same authors, books or articles keep appearing in your reading, make sure to seek them out.

You probably won’t be able to read absolutely everything that has been written on the topic – you’ll have to evaluate which sources are most relevant to your questions.

For each publication, ask yourself:

  • What question or problem is the author addressing?
  • What are the key concepts and how are they defined?
  • What are the key theories, models and methods? Does the research use established frameworks or take an innovative approach?
  • What are the results and conclusions of the study?
  • How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
  • How does the publication contribute to your understanding of the topic? What are its key insights and arguments?
  • What are the strengths and weaknesses of the research?

Make sure the sources you use are credible, and make sure you read any landmark studies and major theories in your field of research.

You can find out how many times an article has been cited on Google Scholar – a high citation count means the article has been influential in the field, and should certainly be included in your literature review.

The scope of your review will depend on your topic and discipline: in the sciences you usually only review recent literature, but in the humanities you might take a long historical perspective (for example, to trace how a concept has changed in meaning over time).

Remember that you can use our template to summarise and evaluate sources you’re thinking about using!

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It’s important to keep track of your sources with references to avoid plagiarism . It can be helpful to make an annotated bibliography, where you compile full reference information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

You can use our free APA Reference Generator for quick, correct, consistent citations.

To begin organising your literature review’s argument and structure, you need to understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

  • Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
  • Themes: what questions or concepts recur across the literature?
  • Debates, conflicts and contradictions: where do sources disagree?
  • Pivotal publications: are there any influential theories or studies that changed the direction of the field?
  • Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

  • Most research has focused on young women.
  • There is an increasing interest in the visual aspects of social media.
  • But there is still a lack of robust research on highly-visual platforms like Instagram and Snapchat – this is a gap that you could address in your own research.

There are various approaches to organising the body of a literature review. You should have a rough idea of your strategy before you start writing.

Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarising sources in order.

Try to analyse patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organise your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

  • Look at what results have emerged in qualitative versus quantitative research
  • Discuss how the topic has been approached by empirical versus theoretical scholarship
  • Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text, your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

If you are writing the literature review as part of your dissertation or thesis, reiterate your central problem or research question and give a brief summary of the scholarly context. You can emphasise the timeliness of the topic (“many recent studies have focused on the problem of x”) or highlight a gap in the literature (“while there has been much research on x, few researchers have taken y into consideration”).

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, make sure to follow these tips:

  • Summarise and synthesise: give an overview of the main points of each source and combine them into a coherent whole.
  • Analyse and interpret: don’t just paraphrase other researchers – add your own interpretations, discussing the significance of findings in relation to the literature as a whole.
  • Critically evaluate: mention the strengths and weaknesses of your sources.
  • Write in well-structured paragraphs: use transitions and topic sentences to draw connections, comparisons and contrasts.

In the conclusion, you should summarise the key findings you have taken from the literature and emphasise their significance.

If the literature review is part of your dissertation or thesis, reiterate how your research addresses gaps and contributes new knowledge, or discuss how you have drawn on existing theories and methods to build a framework for your research. This can lead directly into your methodology section.

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a dissertation , thesis, research paper , or proposal .

There are several reasons to conduct a literature review at the beginning of a research project:

  • To familiarise yourself with the current state of knowledge on your topic
  • To ensure that you’re not just repeating what others have already done
  • To identify gaps in knowledge and unresolved problems that your research can address
  • To develop your theoretical framework and methodology
  • To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your  dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

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What is a literature review?

A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.  That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment.  Rely heavily on the guidelines your instructor has given you.

Why is it important?

A literature review is important because it:

  • Explains the background of research on a topic.
  • Demonstrates why a topic is significant to a subject area.
  • Discovers relationships between research studies/ideas.
  • Identifies major themes, concepts, and researchers on a topic.
  • Identifies critical gaps and points of disagreement.
  • Discusses further research questions that logically come out of the previous studies.

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1. Choose a topic. Define your research question.

Your literature review should be guided by your central research question.  The literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.

  • Make sure your research question is not too broad or too narrow.  Is it manageable?
  • Begin writing down terms that are related to your question. These will be useful for searches later.
  • If you have the opportunity, discuss your topic with your professor and your class mates.

2. Decide on the scope of your review

How many studies do you need to look at? How comprehensive should it be? How many years should it cover? 

  • This may depend on your assignment.  How many sources does the assignment require?

3. Select the databases you will use to conduct your searches.

Make a list of the databases you will search. 

Where to find databases:

  • use the tabs on this guide
  • Find other databases in the Nursing Information Resources web page
  • More on the Medical Library web page
  • ... and more on the Yale University Library web page

4. Conduct your searches to find the evidence. Keep track of your searches.

  • Use the key words in your question, as well as synonyms for those words, as terms in your search. Use the database tutorials for help.
  • Save the searches in the databases. This saves time when you want to redo, or modify, the searches. It is also helpful to use as a guide is the searches are not finding any useful results.
  • Review the abstracts of research studies carefully. This will save you time.
  • Use the bibliographies and references of research studies you find to locate others.
  • Check with your professor, or a subject expert in the field, if you are missing any key works in the field.
  • Ask your librarian for help at any time.
  • Use a citation manager, such as EndNote as the repository for your citations. See the EndNote tutorials for help.

Review the literature

Some questions to help you analyze the research:

  • What was the research question of the study you are reviewing? What were the authors trying to discover?
  • Was the research funded by a source that could influence the findings?
  • What were the research methodologies? Analyze its literature review, the samples and variables used, the results, and the conclusions.
  • Does the research seem to be complete? Could it have been conducted more soundly? What further questions does it raise?
  • If there are conflicting studies, why do you think that is?
  • How are the authors viewed in the field? Has this study been cited? If so, how has it been analyzed?

Tips: 

  • Review the abstracts carefully.  
  • Keep careful notes so that you may track your thought processes during the research process.
  • Create a matrix of the studies for easy analysis, and synthesis, across all of the studies.
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Literature Reviews

What this handout is about.

This handout will explain what literature reviews are and offer insights into the form and construction of literature reviews in the humanities, social sciences, and sciences.

Introduction

OK. You’ve got to write a literature review. You dust off a novel and a book of poetry, settle down in your chair, and get ready to issue a “thumbs up” or “thumbs down” as you leaf through the pages. “Literature review” done. Right?

Wrong! The “literature” of a literature review refers to any collection of materials on a topic, not necessarily the great literary texts of the world. “Literature” could be anything from a set of government pamphlets on British colonial methods in Africa to scholarly articles on the treatment of a torn ACL. And a review does not necessarily mean that your reader wants you to give your personal opinion on whether or not you liked these sources.

What is a literature review, then?

A literature review discusses published information in a particular subject area, and sometimes information in a particular subject area within a certain time period.

A literature review can be just a simple summary of the sources, but it usually has an organizational pattern and combines both summary and synthesis. A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information. It might give a new interpretation of old material or combine new with old interpretations. Or it might trace the intellectual progression of the field, including major debates. And depending on the situation, the literature review may evaluate the sources and advise the reader on the most pertinent or relevant.

But how is a literature review different from an academic research paper?

The main focus of an academic research paper is to develop a new argument, and a research paper is likely to contain a literature review as one of its parts. In a research paper, you use the literature as a foundation and as support for a new insight that you contribute. The focus of a literature review, however, is to summarize and synthesize the arguments and ideas of others without adding new contributions.

Why do we write literature reviews?

Literature reviews provide you with a handy guide to a particular topic. If you have limited time to conduct research, literature reviews can give you an overview or act as a stepping stone. For professionals, they are useful reports that keep them up to date with what is current in the field. For scholars, the depth and breadth of the literature review emphasizes the credibility of the writer in his or her field. Literature reviews also provide a solid background for a research paper’s investigation. Comprehensive knowledge of the literature of the field is essential to most research papers.

Who writes these things, anyway?

Literature reviews are written occasionally in the humanities, but mostly in the sciences and social sciences; in experiment and lab reports, they constitute a section of the paper. Sometimes a literature review is written as a paper in itself.

Let’s get to it! What should I do before writing the literature review?

If your assignment is not very specific, seek clarification from your instructor:

  • Roughly how many sources should you include?
  • What types of sources (books, journal articles, websites)?
  • Should you summarize, synthesize, or critique your sources by discussing a common theme or issue?
  • Should you evaluate your sources?
  • Should you provide subheadings and other background information, such as definitions and/or a history?

Find models

Look for other literature reviews in your area of interest or in the discipline and read them to get a sense of the types of themes you might want to look for in your own research or ways to organize your final review. You can simply put the word “review” in your search engine along with your other topic terms to find articles of this type on the Internet or in an electronic database. The bibliography or reference section of sources you’ve already read are also excellent entry points into your own research.

Narrow your topic

There are hundreds or even thousands of articles and books on most areas of study. The narrower your topic, the easier it will be to limit the number of sources you need to read in order to get a good survey of the material. Your instructor will probably not expect you to read everything that’s out there on the topic, but you’ll make your job easier if you first limit your scope.

Keep in mind that UNC Libraries have research guides and to databases relevant to many fields of study. You can reach out to the subject librarian for a consultation: https://library.unc.edu/support/consultations/ .

And don’t forget to tap into your professor’s (or other professors’) knowledge in the field. Ask your professor questions such as: “If you had to read only one book from the 90’s on topic X, what would it be?” Questions such as this help you to find and determine quickly the most seminal pieces in the field.

Consider whether your sources are current

Some disciplines require that you use information that is as current as possible. In the sciences, for instance, treatments for medical problems are constantly changing according to the latest studies. Information even two years old could be obsolete. However, if you are writing a review in the humanities, history, or social sciences, a survey of the history of the literature may be what is needed, because what is important is how perspectives have changed through the years or within a certain time period. Try sorting through some other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to consider what is currently of interest to scholars in this field and what is not.

Strategies for writing the literature review

Find a focus.

A literature review, like a term paper, is usually organized around ideas, not the sources themselves as an annotated bibliography would be organized. This means that you will not just simply list your sources and go into detail about each one of them, one at a time. No. As you read widely but selectively in your topic area, consider instead what themes or issues connect your sources together. Do they present one or different solutions? Is there an aspect of the field that is missing? How well do they present the material and do they portray it according to an appropriate theory? Do they reveal a trend in the field? A raging debate? Pick one of these themes to focus the organization of your review.

Convey it to your reader

A literature review may not have a traditional thesis statement (one that makes an argument), but you do need to tell readers what to expect. Try writing a simple statement that lets the reader know what is your main organizing principle. Here are a couple of examples:

The current trend in treatment for congestive heart failure combines surgery and medicine. More and more cultural studies scholars are accepting popular media as a subject worthy of academic consideration.

Consider organization

You’ve got a focus, and you’ve stated it clearly and directly. Now what is the most effective way of presenting the information? What are the most important topics, subtopics, etc., that your review needs to include? And in what order should you present them? Develop an organization for your review at both a global and local level:

First, cover the basic categories

Just like most academic papers, literature reviews also must contain at least three basic elements: an introduction or background information section; the body of the review containing the discussion of sources; and, finally, a conclusion and/or recommendations section to end the paper. The following provides a brief description of the content of each:

  • Introduction: Gives a quick idea of the topic of the literature review, such as the central theme or organizational pattern.
  • Body: Contains your discussion of sources and is organized either chronologically, thematically, or methodologically (see below for more information on each).
  • Conclusions/Recommendations: Discuss what you have drawn from reviewing literature so far. Where might the discussion proceed?

Organizing the body

Once you have the basic categories in place, then you must consider how you will present the sources themselves within the body of your paper. Create an organizational method to focus this section even further.

To help you come up with an overall organizational framework for your review, consider the following scenario:

You’ve decided to focus your literature review on materials dealing with sperm whales. This is because you’ve just finished reading Moby Dick, and you wonder if that whale’s portrayal is really real. You start with some articles about the physiology of sperm whales in biology journals written in the 1980’s. But these articles refer to some British biological studies performed on whales in the early 18th century. So you check those out. Then you look up a book written in 1968 with information on how sperm whales have been portrayed in other forms of art, such as in Alaskan poetry, in French painting, or on whale bone, as the whale hunters in the late 19th century used to do. This makes you wonder about American whaling methods during the time portrayed in Moby Dick, so you find some academic articles published in the last five years on how accurately Herman Melville portrayed the whaling scene in his novel.

Now consider some typical ways of organizing the sources into a review:

  • Chronological: If your review follows the chronological method, you could write about the materials above according to when they were published. For instance, first you would talk about the British biological studies of the 18th century, then about Moby Dick, published in 1851, then the book on sperm whales in other art (1968), and finally the biology articles (1980s) and the recent articles on American whaling of the 19th century. But there is relatively no continuity among subjects here. And notice that even though the sources on sperm whales in other art and on American whaling are written recently, they are about other subjects/objects that were created much earlier. Thus, the review loses its chronological focus.
  • By publication: Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on biological studies of sperm whales if the progression revealed a change in dissection practices of the researchers who wrote and/or conducted the studies.
  • By trend: A better way to organize the above sources chronologically is to examine the sources under another trend, such as the history of whaling. Then your review would have subsections according to eras within this period. For instance, the review might examine whaling from pre-1600-1699, 1700-1799, and 1800-1899. Under this method, you would combine the recent studies on American whaling in the 19th century with Moby Dick itself in the 1800-1899 category, even though the authors wrote a century apart.
  • Thematic: Thematic reviews of literature are organized around a topic or issue, rather than the progression of time. However, progression of time may still be an important factor in a thematic review. For instance, the sperm whale review could focus on the development of the harpoon for whale hunting. While the study focuses on one topic, harpoon technology, it will still be organized chronologically. The only difference here between a “chronological” and a “thematic” approach is what is emphasized the most: the development of the harpoon or the harpoon technology.But more authentic thematic reviews tend to break away from chronological order. For instance, a thematic review of material on sperm whales might examine how they are portrayed as “evil” in cultural documents. The subsections might include how they are personified, how their proportions are exaggerated, and their behaviors misunderstood. A review organized in this manner would shift between time periods within each section according to the point made.
  • Methodological: A methodological approach differs from the two above in that the focusing factor usually does not have to do with the content of the material. Instead, it focuses on the “methods” of the researcher or writer. For the sperm whale project, one methodological approach would be to look at cultural differences between the portrayal of whales in American, British, and French art work. Or the review might focus on the economic impact of whaling on a community. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed. Once you’ve decided on the organizational method for the body of the review, the sections you need to include in the paper should be easy to figure out. They should arise out of your organizational strategy. In other words, a chronological review would have subsections for each vital time period. A thematic review would have subtopics based upon factors that relate to the theme or issue.

Sometimes, though, you might need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. Put in only what is necessary. Here are a few other sections you might want to consider:

  • Current Situation: Information necessary to understand the topic or focus of the literature review.
  • History: The chronological progression of the field, the literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
  • Methods and/or Standards: The criteria you used to select the sources in your literature review or the way in which you present your information. For instance, you might explain that your review includes only peer-reviewed articles and journals.

Questions for Further Research: What questions about the field has the review sparked? How will you further your research as a result of the review?

Begin composing

Once you’ve settled on a general pattern of organization, you’re ready to write each section. There are a few guidelines you should follow during the writing stage as well. Here is a sample paragraph from a literature review about sexism and language to illuminate the following discussion:

However, other studies have shown that even gender-neutral antecedents are more likely to produce masculine images than feminine ones (Gastil, 1990). Hamilton (1988) asked students to complete sentences that required them to fill in pronouns that agreed with gender-neutral antecedents such as “writer,” “pedestrian,” and “persons.” The students were asked to describe any image they had when writing the sentence. Hamilton found that people imagined 3.3 men to each woman in the masculine “generic” condition and 1.5 men per woman in the unbiased condition. Thus, while ambient sexism accounted for some of the masculine bias, sexist language amplified the effect. (Source: Erika Falk and Jordan Mills, “Why Sexist Language Affects Persuasion: The Role of Homophily, Intended Audience, and Offense,” Women and Language19:2).

Use evidence

In the example above, the writers refer to several other sources when making their point. A literature review in this sense is just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence to show that what you are saying is valid.

Be selective

Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the review’s focus, whether it is thematic, methodological, or chronological.

Use quotes sparingly

Falk and Mills do not use any direct quotes. That is because the survey nature of the literature review does not allow for in-depth discussion or detailed quotes from the text. Some short quotes here and there are okay, though, if you want to emphasize a point, or if what the author said just cannot be rewritten in your own words. Notice that Falk and Mills do quote certain terms that were coined by the author, not common knowledge, or taken directly from the study. But if you find yourself wanting to put in more quotes, check with your instructor.

Summarize and synthesize

Remember to summarize and synthesize your sources within each paragraph as well as throughout the review. The authors here recapitulate important features of Hamilton’s study, but then synthesize it by rephrasing the study’s significance and relating it to their own work.

Keep your own voice

While the literature review presents others’ ideas, your voice (the writer’s) should remain front and center. Notice that Falk and Mills weave references to other sources into their own text, but they still maintain their own voice by starting and ending the paragraph with their own ideas and their own words. The sources support what Falk and Mills are saying.

Use caution when paraphrasing

When paraphrasing a source that is not your own, be sure to represent the author’s information or opinions accurately and in your own words. In the preceding example, Falk and Mills either directly refer in the text to the author of their source, such as Hamilton, or they provide ample notation in the text when the ideas they are mentioning are not their own, for example, Gastil’s. For more information, please see our handout on plagiarism .

Revise, revise, revise

Draft in hand? Now you’re ready to revise. Spending a lot of time revising is a wise idea, because your main objective is to present the material, not the argument. So check over your review again to make sure it follows the assignment and/or your outline. Then, just as you would for most other academic forms of writing, rewrite or rework the language of your review so that you’ve presented your information in the most concise manner possible. Be sure to use terminology familiar to your audience; get rid of unnecessary jargon or slang. Finally, double check that you’ve documented your sources and formatted the review appropriately for your discipline. For tips on the revising and editing process, see our handout on revising drafts .

Works consulted

We consulted these works while writing this handout. This is not a comprehensive list of resources on the handout’s topic, and we encourage you to do your own research to find additional publications. Please do not use this list as a model for the format of your own reference list, as it may not match the citation style you are using. For guidance on formatting citations, please see the UNC Libraries citation tutorial . We revise these tips periodically and welcome feedback.

Anson, Chris M., and Robert A. Schwegler. 2010. The Longman Handbook for Writers and Readers , 6th ed. New York: Longman.

Jones, Robert, Patrick Bizzaro, and Cynthia Selfe. 1997. The Harcourt Brace Guide to Writing in the Disciplines . New York: Harcourt Brace.

Lamb, Sandra E. 1998. How to Write It: A Complete Guide to Everything You’ll Ever Write . Berkeley: Ten Speed Press.

Rosen, Leonard J., and Laurence Behrens. 2003. The Allyn & Bacon Handbook , 5th ed. New York: Longman.

Troyka, Lynn Quittman, and Doug Hesse. 2016. Simon and Schuster Handbook for Writers , 11th ed. London: Pearson.

You may reproduce it for non-commercial use if you use the entire handout and attribute the source: The Writing Center, University of North Carolina at Chapel Hill

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How to Conduct a Literature Review: Literature Reviews - Getting Started

  • Literature Reviews - Getting Started

Steps to Creating a Literature Review

Step 1: Planning your search

Step 2: Selecting a database

Step 3: Conducting your search

Step 4: Evaluating your results

Step 5: Managing your references

What is a Literature Review?

A literature review is a systematic survey of the scholarly literature published on a given topic.  Rather than providing a new research insight, a literature review lays the groundwork for an in-depth research project analyzing previous research. Type of documents surveyed will vary depending on the field, but can include:

  • journal articles,
  • dissertations.

A thorough literature review will also require surveying what librarians call "gray literature," which includes difficult-to-locate documents such as:

  • technical reports
  • government publications
  • working papers

Purpose of the Lit Review

What's the point, purposes of the literature review.

  • Delimit the research problem
  • Avoid fruitless approaches
  • Identify avenues of future research
  • Seek new lines of inquiry
  • Gain methodological insight

Reasons for Conducting a Literature Review

  • Distinguishing what has been done from what needs to be done
  • Discovering important variables relevant to the topic
  • Synthesizing and gaining new perspective
  • Identifying relationships between ideas and practices
  • Establishing the context of the topic
  • Rationalizing the significance of the problem
  • Enhancing and acquiring subject vocabulary
  • Understanding the structure of the subject
  • Relating ideas and theory to applications
  • Identifying main methodologies and research techniques that have been used
  • Placing research in a historical context to show familiarity with state-of-art development

Questions to consider

  • What is the overarching question or problem your literature review seeks to address?
  • How much familiarity do you already have with the field? Are you already familiar with common methodologies or professional vocabularies?
  • What types of strategies or questions have others in your field pursued?
  • How will you synthesize or summarize the information you gather?
  • What do you or others perceive to be lacking in your field?
  • Is your topic broad? How could it be narrowed?
  • Can you articulate why your topic is important in your field?

Adapted from Hart, C. (1998).  Doing a literature review : Releasing the social science research imagination. London: Sage. As cited in Randolph, Justus. “A Guide to Writing the Dissertation Literature Review.” Practical Assessment, Research and Evaluation , 14(13), p. 2.

Acknowledgements

Merinda Hensley gave permision for content to be  borrowed by permission from Literature Review: Demystified LibGuide from the University of  Illnois  at Urbana-Champaign.

Getting Started

Once you've decided what you want to write about you will need to conduct a systematic review of journal literature to establish what has been written in your field.

Databases enable you to combine search terms and locate high quality journal articles, conference papers and proceedings from a wide range of sources. Have a look at the Accessing Databases tab to choose the right one for your subject area. There are links to brief online tutorials or pdf guides to help you with using each of the databases there too.

  • Brilliant for conducting a thorough, systematic & exhaustive search of the literature
  • You can cross concepts together and so be more precise about what you are searching for
  • Some databases (BREI, PsycINFO) include a thesaurus so you can check terminology
  • The results are valid, reliable and authoritative (academic articles)

What about Google?

G o o g l e and G o o g l e Scholar are not the most efficient or effective tools for searching the literature. Here are a few reasons why:

  • You can only narrow searches by date, not subject   • You cannot give words meaning e.g. primary/first   • Links are unstable and not verified and so you may not be able to access the results   • Pdfs look like they are freely available but often they are not

In addition to this, you also need to carefully evaluate all internet resources:

  1. Who authored the information?   2. What expertise does the writer have to comment?   3. What evidence is used? Are there citations in the piece?   4. What genre is the document: journalism, academic paper,blog, polemic?   5. Is the site/document/report funded by an institution?   6. What argument is being made?   7. When was the text produced?   8. Why did this information emerge at this point in history?   9. Who is the audience for this information?   10. What is not being discussed and what are the political consequences of that absence?   (Taken from Brabazon, T. (2006) 'The Google Effect: Googling, blogging, wikis and the flattening of expertise', Libri, v. 56, pp 157-167)

• You may find this guide for evaluating internet resources (compiled by UWE Library Services) useful too

 And finally.... • They retrieve a huge number of results – which wastes valuable time and leads to information overload and frustration!

  • Next: Step 1 >>
  • Last Updated: Sep 12, 2022 11:13 AM
  • URL: https://libguides.oakwood.edu/litreview

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Reference management. Clean and simple.

Literature review

Literature review for thesis

How to write a literature review in 6 steps

How do you write a good literature review? This step-by-step guide on how to write an excellent literature review covers all aspects of planning and writing literature reviews for academic papers and theses.

Systematic literature review

How to write a systematic literature review [9 steps]

How do you write a systematic literature review? What types of systematic literature reviews exist and where do you use them? Learn everything you need to know about a systematic literature review in this guide

Literature review explained

What is a literature review? [with examples]

Not sure what a literature review is? This guide covers the definition, purpose, and format of a literature review.

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  • When and how to update...

When and how to update systematic reviews: consensus and checklist

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Peer review

This article has a correction. please see:.

  • Errata - September 06, 2016
  • Paul Garner , professor 1 ,
  • Sally Hopewell , associate professor 2 ,
  • Jackie Chandler , methods coordinator 3 ,
  • Harriet MacLehose , senior editor 3 ,
  • Elie A Akl , professor 5 6 ,
  • Joseph Beyene , associate professor 7 ,
  • Stephanie Chang , director 8 ,
  • Rachel Churchill , professor 9 ,
  • Karin Dearness , managing editor 10 ,
  • Gordon Guyatt , professor 4 ,
  • Carol Lefebvre , information consultant 11 ,
  • Beth Liles , methodologist 12 ,
  • Rachel Marshall , editor 3 ,
  • Laura Martínez García , researcher 13 ,
  • Chris Mavergames , head 14 ,
  • Mona Nasser , clinical lecturer in evidence based dentistry 15 ,
  • Amir Qaseem , vice president and chair 16 17 ,
  • Margaret Sampson , librarian 18 ,
  • Karla Soares-Weiser , deputy editor in chief 3 ,
  • Yemisi Takwoingi , senior research fellow in medical statistics 19 ,
  • Lehana Thabane , director and professor 4 20 ,
  • Marialena Trivella , statistician 21 ,
  • Peter Tugwell , professor of medicine, epidemiology, and community medicine 22 ,
  • Emma Welsh , managing editor 23 ,
  • Ed C Wilson , senior research associate in health economics 24 ,
  • Holger J Schünemann , professor 4 5
  • 1 Cochrane Infectious Diseases Group, Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
  • 2 Oxford Clinical Trials Research Unit, University of Oxford, Oxford, UK
  • 3 Cochrane Editorial Unit, Cochrane Central Executive, London, UK
  • 4 Department of Clinical Epidemiology and Biostatistics and Department of Medicine, McMaster University, Hamilton, ON, Canada
  • 5 Cochrane GRADEing Methods Group, Ottawa, ON, Canada
  • 6 Department of Internal Medicine, American University of Beirut, Beirut, Lebanon
  • 7 Department of Mathematics and Statistics, McMaster University
  • 8 Evidence-based Practice Center Program, Agency for Healthcare and Research Quality, Rockville, MD, USA
  • 9 Centre for Reviews and Dissemination, University of York, York, UK
  • 10 Cochrane Upper Gastrointestinal and Pancreatic Diseases Group, Hamilton, ON, Canada
  • 11 Lefebvre Associates, Oxford, UK
  • 12 Kaiser Permanente National Guideline Program, Portland, OR, USA
  • 13 Iberoamerican Cochrane Centre, Barcelona, Spain
  • 14 Cochrane Informatics and Knowledge Management, Cochrane Central Executive, Freiburg, Germany
  • 15 Plymouth University Peninsula School of Dentistry, Plymouth, UK
  • 16 Department of Clinical Policy, American College of Physicians, Philadelphia, PA, USA
  • 17 Guidelines International Network, Pitlochry, UK
  • 18 Children’s Hospital of Eastern Ontario, Ottawa, ON, Canada
  • 19 Institute of Applied Health Research, University of Birmingham, Birmingham, UK
  • 20 Biostatistics Unit, Centre for Evaluation, McMaster University, Hamilton, ON, Canada
  • 21 Centre for Statistics in Medicine, University of Oxford, Oxford, UK
  • 22 University of Ottawa, Ottawa, ON, Canada
  • 23 Cochrane Airways Group, Population Health Research Institute, St George’s, University of London, London, UK
  • 24 Cambridge Centre for Health Services Research, University of Cambridge, Cambridge, UK
  • Correspondence to: P Garner Paul.Garner{at}lstmed.ac.uk
  • Accepted 26 May 2016

Updating of systematic reviews is generally more efficient than starting all over again when new evidence emerges, but to date there has been no clear guidance on how to do this. This guidance helps authors of systematic reviews, commissioners, and editors decide when to update a systematic review, and then how to go about updating the review.

Systematic reviews synthesise relevant research around a particular question. Preparing a systematic review is time and resource consuming, and provides a snapshot of knowledge at the time of incorporation of data from studies identified during the latest search. Newly identified studies can change the conclusion of a review. If they have not been included, this threatens the validity of the review, and, at worst, means the review could mislead. For patients and other healthcare consumers, this means that care and policy development might not be fully informed by the latest research; furthermore, researchers could be misled and carry out research in areas where no further research is actually needed. 1 Thus, there are clear benefits to updating reviews, rather than duplicating the entire process as new evidence emerges or new methods develop. Indeed, there is probably added value to updating a review, because this will include taking into account comments and criticisms, and adoption of new methods in an iterative process. 2 3 4 5 6

Cochrane has over 20 years of experience with preparing and updating systematic reviews, with the publication of over 6000 systematic reviews. However, Cochrane’s principle of keeping all reviews up to date has not been possible, and the organisation has had to adapt: from updating when new evidence becomes available, 7 to updating every two years, 8 to updating based on need and priority. 9 This experience has shown that it is not possible, sensible, or feasible to continually update all reviews all the time. Other groups, including guideline developers and journal editors, adopt updating principles (as applied, for example, by the Systematic Reviews journal; https://systematicreviewsjournal.biomedcentral.com/ ).

The panel for updating guidance for systematic reviews (PUGs) group met to draw together experiences and identify a common approach. The PUGs guidance can help individuals or academic teams working outside of a commissioning agency or Cochrane, who are considering writing a systematic review for a journal or to prepare for a research project. The guidance could also help these groups decide whether their effort is worthwhile.

Summary points

Updating systematic reviews is, in general, more efficient than starting afresh when new evidence emerges. The panel for updating guidance for systematic reviews (PUGs; comprising review authors, editors, statisticians, information specialists, related methodologists, and guideline developers) met to develop guidance for people considering updating systematic reviews. The panel proposed the following:

Decisions about whether and when to update a systematic review are judgments made for individual reviews at a particular time. These decisions can be made by agencies responsible for systematic review portfolios, journal editors with systematic review update services, or author teams considering embarking on an update of a review.

The decision needs to take into account whether the review addresses a current question, uses valid methods, and is well conducted; and whether there are new relevant methods, new studies, or new information on existing included studies. Given this information, the agency, editors, or authors need to judge whether the update will influence the review findings or credibility sufficiently to justify the effort in updating it.

Review authors and commissioners can use a decision framework and checklist to navigate and report these decisions with “update status” and rationale for this status. The panel noted that the incorporation of new synthesis methods (such as Grading of Recommendations Assessment, Development and Evaluation (GRADE)) is also often likely to improve the quality of the analysis and the clarity of the findings.

Given a decision to update, the process needs to start with an appraisal and revision of the background, question, inclusion criteria, and methods of the existing review.

Search strategies should be refined, taking into account changes in the question or inclusion criteria. An analysis of yield from the previous edition, in relation to databases searched, terms, and languages can make searches more specific and efficient.

In many instances, an update represents a new edition of the review, and authorship of the new version needs to follow criteria of the International Committee of Medical Journal Editors (ICMJE). New approaches to publishing licences could help new authors build on and re-use the previous edition while giving appropriate credit to the previous authors.

The panel also reflected on this guidance in the context of emerging technological advances in software, information retrieval, and electronic linkage and mining. With good synthesis and technology partnerships, these advances could revolutionise the efficiency of updating in the coming years.

Panel selection and procedures

An international panel of authors, editors, clinicians, statisticians, information specialists, other methodologists, and guideline developers was invited to a two day workshop at McMaster University, Hamilton, Canada, on 26-27 June 2014, organised by Cochrane. The organising committee selected the panel (web appendix 1). The organising committee invited participants, put forward the agenda, collected background materials and literature, and drafted the structure of the report.

The purpose of the workshop was to develop a common approach to updating systematic reviews, drawing on existing strategies, research, and experience of people working in this area. The selection of participants aimed on broad representation of different groups involved in producing systematic reviews (including authors, editors, statisticians, information specialists, and other methodologists), and those using the reviews (guideline developers and clinicians). Participants within these groups were selected on their expertise and experience in updating, in previous work developing methods to assess reviews, and because some were recognised for developing approaches within organisations to manage updating strategically. We sought to identify general approaches in this area, and not be specific to Cochrane; although inevitably most of the panel were somehow engaged in Cochrane.

The workshop structure followed a series of short presentations addressing key questions on whether, when, and how to update systematic reviews. The proceedings included the management of authorship and editorial decisions, and innovative and technological approaches. A series of small group discussions followed each question, deliberating content, and forming recommendations, as well as recognising uncertainties. Large group, round table discussions deliberated further these small group developments. Recommendations were presented to an invited forum of individuals with varying levels of expertise in systematic reviews from McMaster University (of over 40 people), widely known for its contributions to the field of research evidence synthesis. Their comments helped inform the emerging guidance.

The organising committee became the writing committee after the meeting. They developed the guidance arising from the meeting, developed the checklist and diagrams, added examples, and finalised the manuscript. The guidance was circulated to the larger group three times, with the PUGs panel providing extensive feedback. This feedback was all considered and carefully addressed by the writing committee. The writing committee provided the panel with the option of expressing any additional comments from the general or specific guidance in the report, and the option for registering their own view that might differ to the guidance formed and their view would be recorded in an annex. In the event, consensus was reached, and the annex was not required.

Definition of update

The PUGs panel defined an update of a systematic review as a new edition of a published systematic review with changes that can include new data, new methods, or new analyses to the previous edition. This expands on a previous definition of a systematic review update. 10 An update asks a similar question with regard to the participants, intervention, comparisons, and outcomes (PICO) and has similar objectives; thus it has similar inclusion criteria. These inclusion criteria can be modified in the light of developments within the topic area with new interventions, new standards, and new approaches. Updates will include a new search for potentially relevant studies and incorporate any eligible studies or data; and adjust the findings and conclusions as appropriate. Box 1 provides some examples.

Box 1: Examples of what factors might change in an updated systematic review

A systematic review of steroid treatment in tuberculosis meningitis used GRADE methods and split the composite outcome in the original review of death plus disability into its two components. This improved the clarity of the reviews findings in relation to the effects and the importance of the effects of steroids on death and on disability. 11

A systematic review of dihydroartemisinin-piperaquine (DHAP) for treating malaria was updated with much more detailed analysis of the adverse effect data from the existing trials as a result of questions raised by the European Medicines Agency. Because the original review included other comparisons, the update required extracting only the DHAP comparisons from the original review, and a modification of the title and the PICO. 12

A systematic review of atorvastatin was updated with simple uncontrolled studies. 13 This update allowed comparisons with trials and strengthened the review findings. 14

Which systematic reviews should be updated and when?

Any group maintaining a portfolio of systematic reviews as part of their normative work, such as guidelines panels or Cochrane review groups, will need to prioritise which reviews to update. Box 2 presents the approaches used by the Agency for HealthCare Research and Quality (AHRQ) and Cochrane to prioritise which systematic reviews to update and when. Clearly, the responsibility for deciding which systematic reviews should be updated and when they will be updated will vary: it may be centrally organised and resourced, as with the AHRQ scientific resource centre (box 2). In Cochrane, the decision making process is decentralised to the Cochrane Review Group editorial team, with different approaches applied, often informally.

Box 2: Examples of how different organisations decide on updating systematic reviews

Agency for healthcare research and quality (us).

The AHRQ uses a needs based approach; updating systematic reviews depends on an assessment of several criteria:

Stakeholder impact

Interest from stakeholder partners (such as consumers, funders, guideline developers, clinical societies, James Lind Alliance)

Use and uptake (for example, frequency of citations and downloads)

Citation in scientific literature including clinical practice guidelines

Currency and need for update

New research is available

Review conclusions are probably dated

Update decision

Based on the above criteria, the decision is made to either update, archive, or continue surveillance.

Of over 50 Cochrane editorial teams, most but not all have some systems for updating, although this process can be informal and loosely applied. Most editorial teams draw on some or all of the following criteria:

Strategic importance

Is the topic a priority area (for example, in current debates or considered by guidelines groups)?

Is there important new information available?

Practicalities in organising the update that many groups take into account

Size of the task (size and quality of the review, and how many new studies or analyses are needed)

Availability and willingness of the author team

Impact of update

New research impact on findings and credibility

Consider whether new methods will improve review quality

Priority to update, postpone update, class review as no longer requiring an update

The PUGs panel recommended an individualised approach to updating, which used the procedures summarised in figure 1 ⇓ . The figure provides a status category, and some options for classifying reviews into each of these categories, and builds on a previous decision tool and earlier work developing an updating classification system. 15 16 We provide a narrative for each step.

Fig 1 Decision framework to assess systematic reviews for updating, with standard terms to report such decisions

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Step 1: assess currency

Does the published review still address a current question.

An update is only worthwhile if the question is topical for decision making for practice, policy, or research priorities (fig 1 ⇑ ). For agencies, people responsible for managing a portfolio of systematic reviews, there is a need to use both formal and informal horizon scanning. This type of scanning helps identify questions with currency, and can help identify those reviews that should be updated. The process could include monitoring policy debates around the review, media outlets, scientific (and professional) publications, and linking with guideline developers.

Has the review had good access or use?

Metrics for citations, article access and downloads, and sharing via social or traditional media can be used as proxy or indicators for currency and relevance of the review. Reviews that are widely cited and used could be important to update should the need arise. Comparable reviews that are never cited or rarely downloaded, for example, could indicate that they are not addressing a question that is valued, and might not be worth updating.

In most cases, updated reviews are most useful to stakeholders when there is new information or methods that result in a change in findings. However, there are some circumstances in which an up to date search for information is important for retaining the credibility of the review, regardless of whether the main findings would change or not. For example, key stakeholders would dismiss a review if a study is carried out in a relevant geographical setting but is not included; if a large, high profile study that might not change the findings is not included; or if an up to date search is required for a guideline to achieve credibility. Box 3 provides such examples. If the review does not answer a current question, the intervention has been superseded, then a decision can be made not to update and no further intelligence gathering is required (fig 1 ⇑ ).

Box 3: Examples of a systematic review’s currency

The public is interested in vitamin C for preventing the common cold: the Cochrane review includes over 29 trials with either no or small effects, concluding good evidence of no important effects. 17 Assessment: still a current question for the public.

Low osmolarity oral rehydration salt (ORS) solution versus standard solution for acute diarrhoea in children: the 2001 Cochrane review 18 led the World Health Organization to recommend ORS solution formula worldwide to follow the new ORS solution formula 19 and this has now been accepted globally. Assessment: no longer a current question.

Routine prophylactic antibiotics with caesarean section: the Cochrane review reports clear evidence of maternal benefit from placebo controlled trials but no information on the effects on the baby. 20 Assessment: this is a current question.

A systematic review published in the Lancet examined the effects of artemisinin based combination treatments compared with monotherapy for treating malaria and showed clear benefit. 21 Assessment: this established the treatment globally and is no longer a current question and no update is required.

A Cochrane review of amalgam restorations for dental caries 22 is unlikely to be updated because the use of dental amalgam is declining, and the question is not seen as being important by many dental specialists. Assessment: no longer a current question.

Did the review use valid methods and was it well conducted?

If the question is current and clearly defined, the systematic review needs to have used valid methods and be well conducted. If the review has vague inclusion criteria, poorly articulated outcomes, or inappropriate methods, then updating should not proceed. If the question is current, and the review has been cited or used, then it might be appropriate to simply start with a new protocol. The appraisal should take into account the methods in use when the review was done.

Step 2: identify relevant new methods, studies, and other information

Are there any new relevant methods.

If the question is current, but the review was done some years ago, the quality of the review might not meet current day standards. Methods have advanced quickly, and data extraction and understanding of the review process have become more sophisticated. For example:

Methods for assessing risk of bias of randomised trials, 23 diagnostic test accuracy (QUADAS-2), 24 and observational studies (ROBINS-1). 25

Application of summary of findings, evidence profiles, and related GRADE methods has meant the characteristics of the intervention, characteristics of the participants, and risk of bias are more thoroughly and systematically documented. 26 27

Integration of other study designs containing evidence, such economic evaluation and qualitative research. 28

There are other incremental improvements in a wide range of statistical and methodological areas, for example, in describing and taking into account cluster randomised trials. 29 AMSTAR can assess the overall quality of a systematic review, 30 and the ROBIS tool can provide a more detailed assessment of the potential for bias. 31

Are there any new studies or other information?

If an authoring or commissioning team wants to ensure that a particular review is up to date, there is a need for routine surveillance for new studies that are potentially relevant to the review, by searching and trial register inspection at regular intervals. This process has several approaches, including:

Formal surveillance searching 32

Updating the full search strategies in the original review and running the searches

Tracking studies in clinical trial and other registers

Using literature appraisal services 33

Using a defined abbreviated search strategy for the update 34

Checking studies included in related systematic reviews. 35

How often this surveillance is done, and which approaches to use, depend on the circumstances and the topic. Some topics move quickly, and the definition of “regular intervals” will vary according to the field and according to the state of evidence in the field. For example, early in the life of a new intervention, there might be a plethora of studies, and surveillance would be needed more frequently.

Step 3: assess the effect of updating the review

Will the adoption of new methods change the findings or credibility.

Editors, referees, or experts in the topic area or methodologists can provide an informed view of whether a review can be substantially improved by application of current methodological expectations and new methods (fig 1 ⇑ ). For example, a Cochrane review of iron supplementation in malaria concluded that there was “no significant difference between iron and placebo detected.” 36 An update of the review included a GRADE assessment of the certainty of the evidence, and was able to conclude with a high degree of certainty that iron does not cause an excess of clinical malaria because the upper relative risk confidence intervals of harm was 1.0 with high certainty of evidence. 37

Will the new studies, information, or data change the findings or credibility?

The assessment of new data contained in new studies and how these data might change the review is often used to determine whether an update should go ahead, and the speed with which the update should be conducted. The appraisal of these new data can be carried out in different ways. Initially, methods focused on statistical approaches to predict an overturning of the current review findings in terms of the primary or desired outcome (table 1 ⇓ ). Although this aspect is important, additional studies can add important information to a review, which is more than just changing the primary outcome to a more accurate and reliable estimate. Box 4 gives examples.

Formal prediction tools: how potentially relevant new studies can affect review conclusions

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Box 4: Examples of new information other than new trials being important

The iconic Cochrane review of steroids in preterm labour was thought to provide evidence of benefit in infants, and this question no longer required new trials. However, a new large trial published in the Lancet in 2015 showed that in low and middle income countries, strategies to promote the uptake of neonatal steroids increased neonatal mortality and suspected maternal infection. 49 This information needs to somehow be incorporated into the review to maintain its credibility.

A Cochrane review of community deworming in developing countries indicates that in recent studies, there is little or no effect. 50 The inclusion of a large trial of two million children confirmed that there was no effect on mortality. Although the incorporation of the trial in the review did not change the review’s conclusions, the trial’s absence would have affected the credibility of the review, so it was therefore updated.

A new paper reporting long term follow-up data on anthracycline chemotherapy as part of cancer treatment was published. Although the effects from the outcomes remained essentially unchanged, apart from this longer follow-up, the paper also included information about the performance bias in the original trial, shifting the risk of bias for several outcomes from “unknown” to “high” in the Cochrane review. 51

Reviews with a high level of certainty in the results (that is, when the GRADE assessment for the body of evidence is high) are less likely to change even with the addition of new studies, information, or data, by definition. GRADE can help guide priorities in whether to update, but it is still important to assess new studies that might meet the inclusion criteria. New studies can show unexpected effects (eg, attenuation of efficacy) or provide new information about the effects seen in different circumstances (eg, groups of patients or locations).

Other tools are specifically designed to help decision making in updating. For example, the Ottawa 39 and RAND 45 methods focus on identification of new evidence, the statistical predication tool 15 calculates the probability of new evidence changing the review conclusion, and the value of information analysis approach 52 calculates the expected health gain (table 1 ⇑ ). As yet, there has been limited external validation of these tools to determine which approach would be most effective and when.

If potentially relevant studies are identified that have not previously been assessed for inclusion, authors or those managing the updating process need to assess whether including them might affect the conclusions of the review. They need to examine the weight and certainty of the new evidence to help determine whether an update is needed and how urgent that update is. The updating team can assess this informally by judging whether new studies or data are likely to substantively affect the review, for example, by altering the certainty in an existing comparison, or by generating new comparisons and analyses in the existing review.

New information can also include fresh follow-up data on existing included studies, or information on how the studies were carried out. These should be assessed in terms of whether they might change the review findings or improve its credibility (fig 1 ⇑ ). Indeed, if any study has been retracted, it is important the authors assess the reasons for its retraction. In the case of data fabrication, the study needs to be removed from the analysis and this recorded. A decision needs to be made as to whether other studies by the same author should be removed from the review and other related reviews. An investigation should also be initiated following guidelines from the Committee on Publication Ethics (COPE). Additional published and unpublished data can become available from a wide range of sources—including study investigators, regulatory agencies and industry—and are important to consider.

Preparing for an update

Refresh background, objectives, inclusion criteria, and methods

Before including new studies in the review, authors need to revisit the background, objectives, inclusion criteria, and methods of the current review. In Cochrane, this is referred to as the protocol, and editors are part of this process. The update could range from simply endorsing the current question and inclusion criteria, through to full rewriting of the question, inclusion criteria and methods, and republishing the protocol. As a field progresses with larger and better quality trials rigorously testing the questions posed, it may be appropriate to exclude weaker study designs (such as quasi-randomised comparisons or very small trials) from the update (table 2 ⇓ ). The PUGs panel recommended that a protocol refresh will require the authors to use the latest accepted methods of synthesis, even if this means repeating data extraction for all studies.

New authors and authorship

Updated systematic reviews are new publications with new citations. An authorship team publishing an update in a scientific or medical journal is likely to manage the new edition of a review in the same way as with any other publication, and follow the ICMJE authorship criteria. 56 If the previous author or author team steps down, then they should be acknowledged in the new version. However, some might perceive that their efforts in the first version warrant continued authorship, which may be valid. The management of authorship between versions can sometimes be complicated. At worst, it delays new authors completing an update and leads to long authorship lists of people from previous versions who probably do not meet ICMJE authorship criteria. One approach with updates including new authors is to have an opt-in policy for the existing authors: they can opt in to the new edition, provided that they make clear their contribution, and this is then agreed with the entire author team.

Although they are new publications, updates will generally include content from the published version. Changing licensing rights around systematic reviews to allow new authors of future updates to remix, tweak, or build on the contributions of the original authors of the published version (similar to the rights available via a Creative Commons licence; https://creativecommons.org ) could be a more sustainable and simpler approach. This approach would allow systematic reviews to continue to evolve and build on the work of a range of authors over time, and for contributors to be given credit for contributions to this previous work.

Efficient searching

In performing an update, a search based on the search conducted for the original review is required. The updated search strategy will need to take into account changes in the review question or inclusion criteria, for example, and might be further adjusted based on knowledge of running the original search strategy. The search strategy for an update need not replicate the original search strategy, but could be refined, for example, based on an analysis of the yield of the original search. These new search approaches are currently undergoing formal empirical evaluation, but they may well provide much more efficient search strategies in the future. Some examples of these possible new methods for review updates are described in web appendix 2.

In reporting the search process for the update, investigators must ensure transparency for any previous versions and the current update, and use an adapted flow diagram based on PRISMA reporting (preferred reporting items for systematic reviews and meta-analyses). 57 The search processes and strategies for the update must be adequately reported such that they could be replicated.

Systematic reviews published for the first time in peer reviewed journals are by definition peer reviewed, but practice for updates remains variable, because an update might have few changes (such as an updated search but no new studies found and therefore included) or many changes (such as revise methods and inclusion of several new studies leading to revised conclusions). Therefore, and to use peer reviewers’ time most effectively, editors need to consider when to peer review an update and the type of peer reviewer most useful for a particular update (for example, topic specialist, methodologist). The decision to use peer review, and the number and expertise of the peer reviewers could depend on the nature of the update and the extent of any changes to the systematic review as part of an editor assessment. A change in the date of the search only (where no new studies were identified) would not require peer review (except, arguably, peer review of the search), but the addition of studies that lead to a change in conclusions or significant changes to the methods would require peer review. The nature of the peer review could be described within the published article.

Reporting changes

Authors should provide a clear description of the changes in approach or methods between different editions of a review. Also, authors need to report the differences in findings between the original and updated edition to help users decide how to use the new edition. The approach or format used to present the differences in findings might vary with the target user group. 58 Publishers need to ensure that all previous versions of the review remain publically accessible.

Updates can range from small adjustments to reviews being completely rewritten, and the PUGs panel spent some time debating whether the term “new edition” would be a better description than “update.” However, the word “update” is now in common parlance and changing the term, the panel judged, could cause confusion. However, the debate does illustrate that an update could represent a review that asks a similar question but has been completely revised.

Technology and innovation

The updating of systematic review is generally done manually and is time consuming. There are opportunities to make better use of technology to streamline the updating process and improve efficiency (table 3 ⇓ ). Some of these tools already exist and are in development or in early use, and some are commercially available or freely available. The AHRQ’s evidence based practice centre team has recently published tools for searching and screening, and will provide an assessment of the use, reliability, and availability of these tools. 63

Technological innovations to improve the efficiency of updating systematic reviews

Other developments, such as targeted updates that are performed rapidly and focus on updating only key components of a review, could provide different approaches to updating in the future and are being piloted and evaluated. 64 With implementation of these various innovations, the longer term goal is for “living” systematic reviews, which identify and incorporate information rapidly as it evolves over time. 60

Concluding remarks

Updating systematic reviews, rather than addressing the same question with a fresh protocol, is generally more efficient and allows incremental improvement over time. Mechanical rules appear unworkable, but there is no clear unified approach on when to update, and how implement this. This PUGs panel of authors, editors, statisticians, information specialists, other methodologists, and guideline developers brought together current thinking and experience in this area to provide guidance.

Decisions about whether and when to update a systematic review are judgments made at a point in time. They depend on the currency of the question asked, the need for updating to maintain credibility, the availability of new evidence, and whether new research or new methods will affect the findings.

Whether the review uses current methodological standards is important in deciding if the update will influence the review findings, quality, reliability, or credibility sufficiently to justify the effort in updating it. Those updating systematic reviews to author clinical practice guidelines might consider the influence of new study results in potentially overturning the conclusions of an existing review. Yet, even in cases where new study findings do not change the primary outcome measure, new studies can carry important information about subgroup effects, duration of treatment effects, and other relevant clinical information, enhancing the currency and breadth of review results.

An update requires appraisal and revision of the background, question, inclusion criteria, and methods of the existing review and the existing certainty in the evidence. In particular, methods might need to be updated, and search strategies reconsidered. Authors of updates need to consider inputs to the current edition, and follow ICMJE criteria regarding authorship. 56

The PUGs panel proposed a decision framework (fig 1 ⇑ ), with terms and categories for reporting the decisions made for updating procedures for adoption by Cochrane and other stakeholders. This framework includes journals publishing systematic review updates and independent authors considering updates of existing published reviews. The panel developed a checklist to help judgements about when and how to update.

The current emphasis of authors, guideline developers, Cochrane, and consequently this guidance has been on effects reviews. The checklists and guidance here still applies to other types of systematic reviews, such as those on diagnostic test accuracy, and this guidance will need adapting. Accumulative experience and methods development in reviews other than those of effects are likely to help refine guidance in the future.

This guidance could help groups identify and prioritise reviews for updating and hence use their finite resources to greatest effect. Software innovation and new management systems are being developed and in early use to help streamline review updates in the coming years.

Contributors: HJS initiated the workshop. JC, SH, PG, HM, and HJS organised the materials and the agenda. SH wrote up the proceedings. PG wrote the paper from the proceedings and coordinated the development of the final guidance; JC, SH, HM, and HJS were active in the finalising of the guidance. All PUGs authors contributed to three rounds of manuscript revision.

Funding: Attendance at this meeting, for those attendees not directly employed by Cochrane, was not funded by Cochrane beyond the reimbursement of out of pocket expenses for those attendees for whom this was appropriate. Expenses were not reimbursed for US federal government attendees, in line with US government policy. Statements in the manuscript should not be construed as endorsement by the US Agency for Healthcare Research and Quality or the US Department of Health and Human Services.

Competing interests: All participants have a direct or indirect interest in systematic reviews and updating as part of their job or academic career. Most participants contribute to Cochrane, whose mission includes a commitment to the updating of its systematic review portfolio. JC, HM, RM, CM, KS-W, and MT are, or were at that time, employed by the Cochrane Central Executive.

Provenance and peer review: Not commissioned; externally peer reviewed.

This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 3.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/licenses/by/3.0/ .

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how do you know if a literature review is up to date

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Literature reviews, what is a literature review, learning more about how to do a literature review.

  • Planning the Review
  • The Research Question
  • Choosing Where to Search
  • Organizing the Review
  • Writing the Review

A literature review is a review and synthesis of existing research on a topic or research question. A literature review is meant to analyze the scholarly literature, make connections across writings and identify strengths, weaknesses, trends, and missing conversations. A literature review should address different aspects of a topic as it relates to your research question. A literature review goes beyond a description or summary of the literature you have read. 

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What is a Literature Review? How to Write It (with Examples)

literature review

A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process. 

Table of Contents

  • What is the purpose of literature review? 
  • a. Habitat Loss and Species Extinction: 
  • b. Range Shifts and Phenological Changes: 
  • c. Ocean Acidification and Coral Reefs: 
  • d. Adaptive Strategies and Conservation Efforts: 

How to write a good literature review 

  • Choose a Topic and Define the Research Question: 
  • Decide on the Scope of Your Review: 
  • Select Databases for Searches: 
  • Conduct Searches and Keep Track: 
  • Review the Literature: 
  • Organize and Write Your Literature Review: 
  • How to write a literature review faster with Paperpal? 
  • Frequently asked questions 

What is a literature review?

A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.

how do you know if a literature review is up to date

What is the purpose of literature review?

A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2  

1. Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge. 

2. Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field. 

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3. Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research. 

4. Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered. 

5. Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research. 

6. Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature. 

Literature review example

Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic. 

Literature Review on Climate Change Impacts on Biodiversity:

Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies: 

a. Habitat Loss and Species Extinction:

Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements. 

b. Range Shifts and Phenological Changes:

Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources. 

c. Ocean Acidification and Coral Reefs:

The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems. 

d. Adaptive Strategies and Conservation Efforts:

Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning. 

how do you know if a literature review is up to date

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Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements. 

Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review. 

  • Opening Statement: Begin with a general statement about the broader topic and its significance in the field. 
  • Scope and Purpose: Clearly define the scope of your literature review. Explain the specific research question or objective you aim to address. 
  • Organizational Framework: Briefly outline the structure of your literature review, indicating how you will categorize and discuss the existing research. 
  • Significance of the Study: Highlight why your literature review is important and how it contributes to the understanding of the chosen topic. 
  • Thesis Statement: Conclude the introduction with a concise thesis statement that outlines the main argument or perspective you will develop in the body of the literature review. 

Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria. 

  • Organize by Theme or Concept: Group studies that share common themes, concepts, or methodologies. Discuss each theme or concept in detail, summarizing key findings and identifying gaps or areas of disagreement. 
  • Critical Analysis: Evaluate the strengths and weaknesses of each study. Discuss the methodologies used, the quality of evidence, and the overall contribution of each work to the understanding of the topic. 
  • Synthesis of Findings: Synthesize the information from different studies to highlight trends, patterns, or areas of consensus in the literature. 
  • Identification of Gaps: Discuss any gaps or limitations in the existing research and explain how your review contributes to filling these gaps. 
  • Transition between Sections: Provide smooth transitions between different themes or concepts to maintain the flow of your literature review. 

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Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research. 

  • Summary of Key Findings: Recap the main findings from the literature and restate how they contribute to your research question or objective. 
  • Contributions to the Field: Discuss the overall contribution of your literature review to the existing knowledge in the field. 
  • Implications and Applications: Explore the practical implications of the findings and suggest how they might impact future research or practice. 
  • Recommendations for Future Research: Identify areas that require further investigation and propose potential directions for future research in the field. 
  • Final Thoughts: Conclude with a final reflection on the importance of your literature review and its relevance to the broader academic community. 

what is a literature review

Conducting a literature review

Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1  

Choose a Topic and Define the Research Question:

  • Select a topic that is relevant to your field of study. 
  • Clearly define your research question or objective. Determine what specific aspect of the topic do you want to explore? 

Decide on the Scope of Your Review:

  • Determine the timeframe for your literature review. Are you focusing on recent developments, or do you want a historical overview? 
  • Consider the geographical scope. Is your review global, or are you focusing on a specific region? 
  • Define the inclusion and exclusion criteria. What types of sources will you include? Are there specific types of studies or publications you will exclude? 

Select Databases for Searches:

  • Identify relevant databases for your field. Examples include PubMed, IEEE Xplore, Scopus, Web of Science, and Google Scholar. 
  • Consider searching in library catalogs, institutional repositories, and specialized databases related to your topic. 

Conduct Searches and Keep Track:

  • Develop a systematic search strategy using keywords, Boolean operators (AND, OR, NOT), and other search techniques. 
  • Record and document your search strategy for transparency and replicability. 
  • Keep track of the articles, including publication details, abstracts, and links. Use citation management tools like EndNote, Zotero, or Mendeley to organize your references. 

Review the Literature:

  • Evaluate the relevance and quality of each source. Consider the methodology, sample size, and results of studies. 
  • Organize the literature by themes or key concepts. Identify patterns, trends, and gaps in the existing research. 
  • Summarize key findings and arguments from each source. Compare and contrast different perspectives. 
  • Identify areas where there is a consensus in the literature and where there are conflicting opinions. 
  • Provide critical analysis and synthesis of the literature. What are the strengths and weaknesses of existing research? 

Organize and Write Your Literature Review:

  • Literature review outline should be based on themes, chronological order, or methodological approaches. 
  • Write a clear and coherent narrative that synthesizes the information gathered. 
  • Use proper citations for each source and ensure consistency in your citation style (APA, MLA, Chicago, etc.). 
  • Conclude your literature review by summarizing key findings, identifying gaps, and suggesting areas for future research. 

Whether you’re exploring a new research field or finding new angles to develop an existing topic, sifting through hundreds of papers can take more time than you have to spare. But what if you could find science-backed insights with verified citations in seconds? That’s the power of Paperpal’s new Research feature!  

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Here’s how to use the Research feature:  

  • Ask a question: Get started with a new document on paperpal.com. Click on the “Research” feature and type your question in plain English. Paperpal will scour over 250 million research articles, including conference papers and preprints, to provide you with accurate insights and citations. 
  • Review and Save: Paperpal summarizes the information, while citing sources and listing relevant reads. You can quickly scan the results to identify relevant references and save these directly to your built-in citations library for later access. 
  • Cite with Confidence: Paperpal makes it easy to incorporate relevant citations and references into your writing, ensuring your arguments are well-supported by credible sources. This translates to a polished, well-researched literature review. 

The literature review sample and detailed advice on writing and conducting a review will help you produce a well-structured report. But remember that a good literature review is an ongoing process, and it may be necessary to revisit and update it as your research progresses. By combining effortless research with an easy citation process, Paperpal Research streamlines the literature review process and empowers you to write faster and with more confidence. Try Paperpal Research now and see for yourself.  

Frequently asked questions

A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.

Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.  

Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic. 

Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods. 

Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers.  Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved.  Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic.  Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings.  Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject.  It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.

The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review:  Introduction:   Provide an overview of the topic.  Define the scope and purpose of the literature review.  State the research question or objective.  Body:   Organize the literature by themes, concepts, or chronology.  Critically analyze and evaluate each source.  Discuss the strengths and weaknesses of the studies.  Highlight any methodological limitations or biases.  Identify patterns, connections, or contradictions in the existing research.  Conclusion:   Summarize the key points discussed in the literature review.  Highlight the research gap.  Address the research question or objective stated in the introduction.  Highlight the contributions of the review and suggest directions for future research.

Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows: 

References 

  • Denney, A. S., & Tewksbury, R. (2013). How to write a literature review.  Journal of criminal justice education ,  24 (2), 218-234. 
  • Pan, M. L. (2016).  Preparing literature reviews: Qualitative and quantitative approaches . Taylor & Francis. 
  • Cantero, C. (2019). How to write a literature review.  San José State University Writing Center . 

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Charles Sturt University

Literature Review: Keeping up to date with literature

  • Traditional or narrative literature reviews
  • Scoping Reviews
  • Systematic literature reviews
  • Annotated bibliography
  • Keeping up to date with literature
  • Finding a thesis
  • Evaluating sources and critical appraisal of literature
  • Managing and analysing your literature
  • Further reading and resources

From literature review to HDR Thesis

You have developed strategies, searched databases and written your literature review. You have a very good understanding of your research question and how you are going to proceed with your research for your Higher Degree Research Thesis. However, this may take several years to complete and you will need to know what is happening in your field of research while you are completing your own research. To do this you can save your searches as alerts so that when an article is published that matches your search criteria you will receive an email to notify you of its existence.

Table of Contents Alerts

A table of contents (TOC) alert, journal alert and publication alert will notify you when a new issue of a journal is published. By subscribing to these services you will receive an email when a new issue is published containing the table of contents. This can help you to stay up to date with current research relevant to your topic. Most journal databases will provide TOC alerts.

  • EBSCO databases - click on the "Publications' link in the top toolbar. Browse for the journal title and select. Click on the 'create journal alert" icon next to the title of the journal  (you will need to sign in to send e-mail alerts)
  • ProQuest databases - You will need to create a personal 'My Research' account and sign in. Then click on the 'Publications' link in the top toolbar. Search for the journal and click on the title. Then click on 'Set up alert'.
  • Web of Science

Topic or subject alerts

Subject alerts allow you to be notified when articles are published that match your subject criteria. After you have developed a search strategy and executed the search, you set up an alert to be notified of any new articles that get added to the database that match your search strategy.

A search alert will be sent to you after you have saved a database search that you run periodically.

The following databases support Table of Contents (ToC) and search alerts.

  • How to use Journal TOC alert
  • How to use Search alerts
  • Create a Publication alert
  • Create a Search alert
  • ScienceDirect
  • Taylor & Francis Online
  • Journal alerts
  • Citation alerts
  • Research Professional

Citation Alerts

A citation alert notifies you when new publications cite a particular paper.

Citation alerts can be created for Web of Science and Scopus .

Research Office Bulletin

The Office of Research Services and Graduate Studies publish a monthly bulletin which aims to bring together a range of information from across the CSU Research Community including :

  • Events  
  • Funding & Other Opportunities
  • Professional Development
  • Success Stories
  • Support available
  • Tips and Information
  • Featured Stories
  • << Previous: Developing a search strategy
  • Next: Where to search >>
  • Last Updated: May 12, 2024 12:18 PM
  • URL: https://libguides.csu.edu.au/review

Acknowledgement of Country

Charles Sturt University is an Australian University, TEQSA Provider Identification: PRV12018. CRICOS Provider: 00005F.

Grad Coach

What Is A Literature Review?

A plain-language explainer (with examples).

By:  Derek Jansen (MBA) & Kerryn Warren (PhD) | June 2020 (Updated May 2023)

If you’re faced with writing a dissertation or thesis, chances are you’ve encountered the term “literature review” . If you’re on this page, you’re probably not 100% what the literature review is all about. The good news is that you’ve come to the right place.

Literature Review 101

  • What (exactly) is a literature review
  • What’s the purpose of the literature review chapter
  • How to find high-quality resources
  • How to structure your literature review chapter
  • Example of an actual literature review

What is a literature review?

The word “literature review” can refer to two related things that are part of the broader literature review process. The first is the task of  reviewing the literature  – i.e. sourcing and reading through the existing research relating to your research topic. The second is the  actual chapter  that you write up in your dissertation, thesis or research project. Let’s look at each of them:

Reviewing the literature

The first step of any literature review is to hunt down and  read through the existing research  that’s relevant to your research topic. To do this, you’ll use a combination of tools (we’ll discuss some of these later) to find journal articles, books, ebooks, research reports, dissertations, theses and any other credible sources of information that relate to your topic. You’ll then  summarise and catalogue these  for easy reference when you write up your literature review chapter. 

The literature review chapter

The second step of the literature review is to write the actual literature review chapter (this is usually the second chapter in a typical dissertation or thesis structure ). At the simplest level, the literature review chapter is an  overview of the key literature  that’s relevant to your research topic. This chapter should provide a smooth-flowing discussion of what research has already been done, what is known, what is unknown and what is contested in relation to your research topic. So, you can think of it as an  integrated review of the state of knowledge  around your research topic. 

Starting point for the literature review

What’s the purpose of a literature review?

The literature review chapter has a few important functions within your dissertation, thesis or research project. Let’s take a look at these:

Purpose #1 – Demonstrate your topic knowledge

The first function of the literature review chapter is, quite simply, to show the reader (or marker) that you  know what you’re talking about . In other words, a good literature review chapter demonstrates that you’ve read the relevant existing research and understand what’s going on – who’s said what, what’s agreed upon, disagreed upon and so on. This needs to be  more than just a summary  of who said what – it needs to integrate the existing research to  show how it all fits together  and what’s missing (which leads us to purpose #2, next). 

Purpose #2 – Reveal the research gap that you’ll fill

The second function of the literature review chapter is to  show what’s currently missing  from the existing research, to lay the foundation for your own research topic. In other words, your literature review chapter needs to show that there are currently “missing pieces” in terms of the bigger puzzle, and that  your study will fill one of those research gaps . By doing this, you are showing that your research topic is original and will help contribute to the body of knowledge. In other words, the literature review helps justify your research topic.  

Purpose #3 – Lay the foundation for your conceptual framework

The third function of the literature review is to form the  basis for a conceptual framework . Not every research topic will necessarily have a conceptual framework, but if your topic does require one, it needs to be rooted in your literature review. 

For example, let’s say your research aims to identify the drivers of a certain outcome – the factors which contribute to burnout in office workers. In this case, you’d likely develop a conceptual framework which details the potential factors (e.g. long hours, excessive stress, etc), as well as the outcome (burnout). Those factors would need to emerge from the literature review chapter – they can’t just come from your gut! 

So, in this case, the literature review chapter would uncover each of the potential factors (based on previous studies about burnout), which would then be modelled into a framework. 

Purpose #4 – To inform your methodology

The fourth function of the literature review is to  inform the choice of methodology  for your own research. As we’ve  discussed on the Grad Coach blog , your choice of methodology will be heavily influenced by your research aims, objectives and questions . Given that you’ll be reviewing studies covering a topic close to yours, it makes sense that you could learn a lot from their (well-considered) methodologies.

So, when you’re reviewing the literature, you’ll need to  pay close attention to the research design , methodology and methods used in similar studies, and use these to inform your methodology. Quite often, you’ll be able to  “borrow” from previous studies . This is especially true for quantitative studies , as you can use previously tried and tested measures and scales. 

Free Webinar: Literature Review 101

How do I find articles for my literature review?

Finding quality journal articles is essential to crafting a rock-solid literature review. As you probably already know, not all research is created equally, and so you need to make sure that your literature review is  built on credible research . 

We could write an entire post on how to find quality literature (actually, we have ), but a good starting point is Google Scholar . Google Scholar is essentially the academic equivalent of Google, using Google’s powerful search capabilities to find relevant journal articles and reports. It certainly doesn’t cover every possible resource, but it’s a very useful way to get started on your literature review journey, as it will very quickly give you a good indication of what the  most popular pieces of research  are in your field.

One downside of Google Scholar is that it’s merely a search engine – that is, it lists the articles, but oftentimes  it doesn’t host the articles . So you’ll often hit a paywall when clicking through to journal websites. 

Thankfully, your university should provide you with access to their library, so you can find the article titles using Google Scholar and then search for them by name in your university’s online library. Your university may also provide you with access to  ResearchGate , which is another great source for existing research. 

Remember, the correct search keywords will be super important to get the right information from the start. So, pay close attention to the keywords used in the journal articles you read and use those keywords to search for more articles. If you can’t find a spoon in the kitchen, you haven’t looked in the right drawer. 

Need a helping hand?

how do you know if a literature review is up to date

How should I structure my literature review?

Unfortunately, there’s no generic universal answer for this one. The structure of your literature review will depend largely on your topic area and your research aims and objectives.

You could potentially structure your literature review chapter according to theme, group, variables , chronologically or per concepts in your field of research. We explain the main approaches to structuring your literature review here . You can also download a copy of our free literature review template to help you establish an initial structure.

In general, it’s also a good idea to start wide (i.e. the big-picture-level) and then narrow down, ending your literature review close to your research questions . However, there’s no universal one “right way” to structure your literature review. The most important thing is not to discuss your sources one after the other like a list – as we touched on earlier, your literature review needs to synthesise the research , not summarise it .

Ultimately, you need to craft your literature review so that it conveys the most important information effectively – it needs to tell a logical story in a digestible way. It’s no use starting off with highly technical terms and then only explaining what these terms mean later. Always assume your reader is not a subject matter expert and hold their hand through a journe y of the literature while keeping the functions of the literature review chapter (which we discussed earlier) front of mind.

A good literature review should synthesise the existing research in relation to the research aims, not simply summarise it.

Example of a literature review

In the video below, we walk you through a high-quality literature review from a dissertation that earned full distinction. This will give you a clearer view of what a strong literature review looks like in practice and hopefully provide some inspiration for your own. 

Wrapping Up

In this post, we’ve (hopefully) answered the question, “ what is a literature review? “. We’ve also considered the purpose and functions of the literature review, as well as how to find literature and how to structure the literature review chapter. If you’re keen to learn more, check out the literature review section of the Grad Coach blog , as well as our detailed video post covering how to write a literature review . 

Literature Review Course

Psst… there’s more!

This post is an extract from our bestselling short course, Literature Review Bootcamp . If you want to work smart, you don't want to miss this .

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16 Comments

BECKY NAMULI

Thanks for this review. It narrates what’s not been taught as tutors are always in a early to finish their classes.

Derek Jansen

Thanks for the kind words, Becky. Good luck with your literature review 🙂

ELaine

This website is amazing, it really helps break everything down. Thank you, I would have been lost without it.

Timothy T. Chol

This is review is amazing. I benefited from it a lot and hope others visiting this website will benefit too.

Timothy T. Chol [email protected]

Tahir

Thank you very much for the guiding in literature review I learn and benefited a lot this make my journey smooth I’ll recommend this site to my friends

Rosalind Whitworth

This was so useful. Thank you so much.

hassan sakaba

Hi, Concept was explained nicely by both of you. Thanks a lot for sharing it. It will surely help research scholars to start their Research Journey.

Susan

The review is really helpful to me especially during this period of covid-19 pandemic when most universities in my country only offer online classes. Great stuff

Mohamed

Great Brief Explanation, thanks

Mayoga Patrick

So helpful to me as a student

Amr E. Hassabo

GradCoach is a fantastic site with brilliant and modern minds behind it.. I spent weeks decoding the substantial academic Jargon and grounding my initial steps on the research process, which could be shortened to a couple of days through the Gradcoach. Thanks again!

S. H Bawa

This is an amazing talk. I paved way for myself as a researcher. Thank you GradCoach!

Carol

Well-presented overview of the literature!

Philippa A Becker

This was brilliant. So clear. Thank you

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Literature Review: What is a literature review?

  • What is a literature review?
  • Finding the literature
  • Guidebooks on the literature review
  • Examples of literature reviews

What exactly is a literature review?

A literature review is a summary and critical analysis of the literature on your topic. It is an opportunity for you to identify trends and point out gaps in the literature. Preparing a literature review requires in-depth reading, as well as identification of major methods and failings in the field.

When you undertake a literature review, you first need to identify a research question and then seek to answer this question by searching for and analyzing relevant literature using a systematic approach. This review should then lead you to the development of new insights that are only possible when each piece of relevant information is seen in the context of other information (Aveyard 6). 

Why write a literature review?

Literature reviews are important because they summarize the literature that is available on any one topic. They make sense of a body of research and present an analysis of the available literature so that the reader does not have to access each individual document included in the review (Aveyard  6 ).  In an age when the proliferation of information makes it impossible to know all the literature relevant to a topic or problem,  reviews of existing literature are becoming increasingly important (Moss 209).

In the beginning of a project, a literature review should be undertaken to help you learn more about your topic. It can help you determine if research on the topic is needed and worthwhile, narrow down the topic so you are moving from a general idea to something focused and researchable, and determine the direction for your research so you are building on previous work or filling a gap in the literature ( Leavy  56).

Strategies for writing a literature review

An effective literature review will persuade readers of the need to address a particular question in a particular way. Conversely, without a literature review, the rationale for a study is  frequently less compelling, and the findings are less likely to make an impact on the field. (Mandra sec. 7.2)

  • Why is your question important?  Justify it.
  • What have others said about this topic?  Organize their work thematically.
  • How will you build on or extend previously existing research?  Evaluate & critique it.

Ask yourself these questions in order to evaluate the literature: what are the advantages, limitations, and challenges of pursuing one research method over another?  ​In your literature  review, you can c ategorize  and  class ify  the literature. Summarize the overall theme. What connections exist between the various works? Do you agree with their methods and/or findings? Do they all agree with each other, or is there some disagreement? Where does your project fit and why is it important?

Additionally, try to locate recent research on your  topic so that your review is up to date. A good literature review will also consider landmark studies on the topic, whic h is to say that it may be written by a foundational author who is well known for their work on the topic. Once you've identified one or more seminal authors, see if they have any theories about the topic that can help you frame your approach ( Leavy  57).

Aveyard, Helen. Doing a Literature Review in Health and Social Care: A Practical Guide . 2nd ed. Maidenhead: McGraw-Hill/Open UP, 2010.

Mandra, Meghan McGlinn, and Cheryl Mason Bolick. The Wiley Handbook of Social Studies Research . Chichester, [England]: Wiley Blackwell, 2017.

Leavy, Patricia. Research Design: Quantitative, Qualitative, Mixed-Methods, Arts-Based, and Community-Based Participatory Research Approaches . New York: The Gulford Press, 2017.

Moss, Pamela A., and Edward H. Haertel. “Engaging Methodological Pluralism.” Handbook of Research on Teaching , edited by Drew H. Gitomer and Courtney A. Bell, 5th Edition ed. Washington, DC: American Educational Research Association, 2016. 127–248.

  • Next: Finding the literature >>
  • Last Updated: Nov 7, 2022 8:32 AM
  • URL: https://conncoll.libguides.com/LitReview

IMAGES

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VIDEO

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  3. Janen ki ? জানেন কি? Akshay Kumar Maitreya ke chhilen?@janaajanaosahitya

  4. Janen ki ? জানেন কি? Akshay Kumar Baral ke chilen?@janaajanaosahitya

  5. Janen ki ? জানেন কি? Bal Jack er shhakh ki chhilo?@janaajanaosahitya

  6. Janen ki ? জানেন কি? Madhu kakhana nasta hayna. @janaajanaosahitya

COMMENTS

  1. Ten Simple Rules for Writing a Literature Review

    The topic must at least be: interesting to you (ideally, you should have come across a series of recent papers related to your line of work that call for a critical summary), an important aspect of the field (so that many readers will be interested in the review and there will be enough material to write it), and.

  2. How to Write a Literature Review

    Examples of literature reviews. Step 1 - Search for relevant literature. Step 2 - Evaluate and select sources. Step 3 - Identify themes, debates, and gaps. Step 4 - Outline your literature review's structure. Step 5 - Write your literature review.

  3. Comprehensive Literature Review: A Guide

    Despite their various structures (see the descriptions below), literature reviews consist of the following elements: Citations for the referenced materials. A discussion of the materials' research purpose, methods, and findings. A discussion of how those findings relate to your research. A discussion of the similarities and differences between ...

  4. PDF Conducting a Literature Review

    Literature Review A literature review is a survey of scholarly sources that provides an overview of a particular topic. Literature reviews are a collection of ... keeping up to date during the review process. Data evaluation Determining which literature makes a significant contribution to the understanding of the topic.

  5. Guidance on Conducting a Systematic Literature Review

    Literature review is an essential feature of academic research. Fundamentally, knowledge advancement must be built on prior existing work. To push the knowledge frontier, we must know where the frontier is. By reviewing relevant literature, we understand the breadth and depth of the existing body of work and identify gaps to explore.

  6. Literature Review: The What, Why and How-to Guide

    In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your ...

  7. Writing a Literature Review

    Preparing a literature review involves: Searching for reliable, accurate and up-to-date material on a topic or subject. Reading and summarising the key points from this literature. Synthesising these key ideas, theories and concepts into a summary of what is known. Discussing and evaluating these ideas, theories and concepts.

  8. When and how to update systematic reviews

    When registering a review with the Cochrane Collaboration, the review authors agree to keep it up‐to‐date (Higgins 2005). The Cochrane Collaboration recommends periodic updating of the literature search (e.g., every two years) to determine whether or not relevant new studies are available for inclusion in a previously completed systematic ...

  9. What is a Literature Review?

    A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research. There are five key steps to writing a literature review: Search for relevant literature. Evaluate sources. Identify themes, debates and gaps.

  10. Steps in Conducting a Literature Review

    Review the abstracts of research studies carefully. This will save you time. Use the bibliographies and references of research studies you find to locate others. Check with your professor, or a subject expert in the field, if you are missing any key works in the field. Ask your librarian for help at any time.

  11. Literature Reviews

    History: The chronological progression of the field, the literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology. Methods and/or Standards: The criteria you used to select the sources in your literature review or the way in which you present your information ...

  12. Writing a literature review

    Writing a literature review requires a range of skills to gather, sort, evaluate and summarise peer-reviewed published data into a relevant and informative unbiased narrative. Digital access to research papers, academic texts, review articles, reference databases and public data sets are all sources of information that are available to enrich ...

  13. How to Conduct a Literature Review: Literature Reviews

    A literature review is a systematic survey of the scholarly literature published on a given topic. Rather than providing a new research insight, a literature review lays the groundwork for an in-depth research project analyzing previous research. Type of documents surveyed will vary depending on the field, but can include: books; journal ...

  14. Writing a literature review

    How to write a literature review in 6 steps. How do you write a good literature review? This step-by-step guide on how to write an excellent literature review covers all aspects of planning and writing literature reviews for academic papers and theses.

  15. How To Write A Literature Review

    You need to follow the below-mentioned steps, to write a literature review: 1. Outline and identify the purpose of a literature review. As a first step on how to write a literature review, you must know what the research question or topic is and what shape you want your literature review to take.

  16. When and how to update systematic reviews: consensus and checklist

    Systematic reviews synthesise relevant research around a particular question. Preparing a systematic review is time and resource consuming, and provides a snapshot of knowledge at the time of incorporation of data from studies identified during the latest search. Newly identified studies can change the conclusion of a review.

  17. PDF How Do I Know When My Literature Review Is Finished? Couldn't It Go on

    3. Most important, you and your adviser and colleagues (and whoever else is acting as your mentor) are satisfied that you have comprehen- sively addressed the important issues of the theory underlying the question you are asking as well as the methods. This is a somewhat subjective criterion but very important nonetheless.

  18. What is a Literature Review?

    A literature review is meant to analyze the scholarly literature, make connections across writings and identify strengths, weaknesses, trends, and missing conversations. A literature review should address different aspects of a topic as it relates to your research question. A literature review goes beyond a description or summary of the ...

  19. What is a Literature Review? How to Write It (with Examples)

    A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship ...

  20. Literature Review: Keeping up to date with literature

    This can help you to stay up to date with current research relevant to your topic. Most journal databases will provide TOC alerts. EBSCO databases - click on the "Publications' link in the top toolbar. Browse for the journal title and select. Click on the 'create journal alert" icon next to the title of the journal (you will need to sign in to ...

  21. What Is A Literature Review?

    The word "literature review" can refer to two related things that are part of the broader literature review process. The first is the task of reviewing the literature - i.e. sourcing and reading through the existing research relating to your research topic. The second is the actual chapter that you write up in your dissertation, thesis or ...

  22. What is a literature review?

    A literature review is a summary and critical analysis of the literature on your topic. It is an opportunity for you to identify trends and point out gaps in the literature. Preparing a literature review requires in-depth reading, as well as identification of major methods and failings in the field. When you undertake a literature review, you ...