thesis systematic literature review

How to Do a Systematic Review: A Best Practice Guide for Conducting and Reporting Narrative Reviews, Meta-Analyses, and Meta-Syntheses

Affiliations.

• 1 Behavioural Science Centre, Stirling Management School, University of Stirling, Stirling FK9 4LA, United Kingdom; email: [email protected].
• 2 Department of Psychological and Behavioural Science, London School of Economics and Political Science, London WC2A 2AE, United Kingdom.
• 3 Department of Statistics, Northwestern University, Evanston, Illinois 60208, USA; email: [email protected].
• PMID: 30089228
• DOI: 10.1146/annurev-psych-010418-102803

Systematic reviews are characterized by a methodical and replicable methodology and presentation. They involve a comprehensive search to locate all relevant published and unpublished work on a subject; a systematic integration of search results; and a critique of the extent, nature, and quality of evidence in relation to a particular research question. The best reviews synthesize studies to draw broad theoretical conclusions about what a literature means, linking theory to evidence and evidence to theory. This guide describes how to plan, conduct, organize, and present a systematic review of quantitative (meta-analysis) or qualitative (narrative review, meta-synthesis) information. We outline core standards and principles and describe commonly encountered problems. Although this guide targets psychological scientists, its high level of abstraction makes it potentially relevant to any subject area or discipline. We argue that systematic reviews are a key methodology for clarifying whether and how research findings replicate and for explaining possible inconsistencies, and we call for researchers to conduct systematic reviews to help elucidate whether there is a replication crisis.

Keywords: evidence; guide; meta-analysis; meta-synthesis; narrative; systematic review; theory.

• Guidelines as Topic
• Meta-Analysis as Topic*
• Publication Bias
• Review Literature as Topic
• Systematic Reviews as Topic*

Systematic literature reviews

Systematic approaches to literature review searching.

This guide is primarily for those undertaking a literature review. It outlines how to approach the searching phase systematically in order to identify relevant literature on a research question.

Why be systematic? This approach can:

• Provide a robust overview of the available literature on your topic
• Ensure relevant literature is identified and key publications are not overlooked
• Reduce irrelevant search results through search planning
• Help you to create a reproducible search strategy.

In addition, applying a systematic approach will allow you to work more efficiently.

A literature review may form an essential part of the research process, for example as a major component of a thesis or dissertation. Alternatively, a review may constitute a research project in itself - as a peer-reviewed publication in a journal, or as a report from a research funded project.

While the searching phase of any literature review should be approached in a systematic manner, you do not need to follow all of the techniques outlined in this guide. The methods you choose are dependent on the time and resources you have available, and the purpose of your literature review.

Systematic reviews vs. systematic approaches

A full systematic review aims to comprehensively identify, evaluate and integrate the findings of all relevant studies on a particular research question. A systematic approach involves a rigorous and structured search strategy, without necessarily attempting to include all available research on a particular topic.

Why and how to conduct a systematic literature review

Systematic literature reviews may seem daunting at first, but they offer substantial benefits, especially in enhancing the theoretical framework for your research! Learn more about systematic literature reviews and their benefits. And have a look at a simple step-by-step guide that breaks down the daunting task of conducting a systematic literature review into simple, actionable steps.

What is a systematic literature review?

The difference between a systematic and a regular literature review, the difference between a systematic literature review and a meta-analysis, benefits of conducting a systematic literature review, google scholar to conduct a systematic literature review, web of science to conduct a systematic literature review, scopus to conduct a systematic literature review, step-by-step guide for conducting a systematic literature review.

Systematic literature reviews are a means to rigorously review existing literature on a specific topic. They collect and analyze existing literature in a systematic and replicable way.

Following the definition of a topic of interest and concrete research question, a systematic literature review starts by defining several keywords. Then, academic citation databases are used to retrieve all articles that include these keywords.

Furthermore, inclusion and exclusion criteria for sorting through the existing literature are set up. Think of a time frame, the type of publication (articles, books etc.), a geographic focus, and a disciplinary background. You name it.

Systematic literature reviews are a means to rigorously review existing literature on a specific topic. They collect and analyse existing literature in a systematic and replicable way.

While systematic literature reviews require a lot of work, they can convincingly draw conclusions on the state of the art of existing knowledge, uncover research gaps, and support the creation of new theoretical and conceptual frameworks.

In a systematic literature review, inclusion and exclusion criteria for sorting through the existing literature are set up. Think of a time frame, the type of publication (articles, books etc.), a geographic focus, and a disciplinary background.

Therefore, systematic literature reviews are crystal clear about the process of collecting and analyzing literature, which makes them replicable.

Before starting to consider whether a systematic literature review is right for you, it is important to be aware of the main differences between systematic and regular literature reviews.

The main differences between a systematic and a regular literature review are the process of collecting and analyzing literature, the accuracy of claims, the scope and replicability.

In a regular literature review, authors select articles or other publications ad hoc, to support the arguments of their work. Authors make claims about the state of the art of academic knowledge on a specific topic, but do not necessarily provide systematic evidence to support their claims.

Therefore, the level of accuracy differs in systematic and regular literature reviews.

Furthermore, authors doing regular literature reviews generally do not explain how they conducted their review, and how they selected relevant literature. Therefore, regular literature reviews are usually not replicable, whereas systematic ones are.

Additionally, the scope of a review differs immensely between systematic and regular literature reviews.

Systematic literature reviews tend to methodically analyze hundreds of articles, whereas regular literature reviews are much more limited in scope and highly selective in their choice of publications that are included.

Systematic literature reviews and meta-analyses are frequently confused or used interchangeably, but it’s important to understand that they are distinct methodologies.

While a meta-analysis focuses on synthesizing data and drawing broad conclusions from multiple studies, a systematic literature review is geared towards answering a well-defined research question with a comprehensive and methodical approach.

A meta-analysis involves the comprehensive analysis of results from multiple studies on a particular topic, aiming to identify patterns and draw generalized conclusions. These analyses often rely on statistical methods to combine data from various sources.

On the other hand, systematic literature reviews can take either a qualitative or quantitative approach. They are designed to address a specific and often novel research question, going beyond a mere summary of existing studies.

Conducting a ‘regular’ literature review is perfectly valid, but there are compelling reasons to consider a systematic literature review for certain research endeavors.

One primary advantage of a systematic review is its ability to address the overwhelming volume of relevant literature that can leave researchers, particularly master’s and PhD students, feeling daunted and unsure of when to stop searching for more material.

By conducting a systematic review, all pertinent literature can be analyzed within specific parameters, alleviating concerns about potentially missing critical information.

Moreover, a systematic literature review offers the advantage of identifying and showcasing research gaps, bolstering the academic significance of one’s work. This comprehensive approach to reviewing existing literature contributes to a stronger foundation for the research and its potential impact.

Additionally, by being transparent and explicit about the methodology employed in collecting and analyzing the literature, researchers enhance the credibility and reliability of their statements and arguments. This explicitness reinforces the trustworthiness of the research findings, which is crucial in the academic world.

Academic citation databases suitable for systematic literature reviews

To conduct systematic literature reviews, it is recommended to utilize a citation database that provides built-in features to refine search queries effectively.

Google Scholar is a widely used search engine among scholars, but its sidebar for limiting search queries is relatively basic. Despite this limitation, the advantage of using Google Scholar is that it is freely accessible to all users, including those without institutional affiliations.

Web of Science has very elaborate search options. The search engine allows you to choose from various databases and indexes, such as the Science Citation Index or the Social Science Citation Index. Additionally, it enables you to search for keywords within topics or titles, as well as author names, affiliations, publication years, and more.

Web of Science provides a wide range of Booleans (depicted in the image below on the right) that you can utilize to precisely specify your search criteria. Booleans are a system of logic employed in programming and computer sciences, featuring operators like “AND,” “OR,” and “NOT.” By using these operators, you can fine-tune your search queries and filter results to precisely match what you are looking for.

After obtaining search results on Web of Science, you have the option to further refine and organize them based on various criteria, such as research areas, disciplines, languages, regions, document types, and more.

Although it may require some time and practice to become proficient in developing precise search queries on Web of Science, the database offers tremendous opportunities for conducting systematic literature reviews. Its extensive filtering and organizing features empower researchers to gather comprehensive and relevant literature on specific topics.

Scopus the citation database by publisher Elsevier, boasts access to over 36,000 journals. Its layout and search options closely resemble those of Web of Science, making it a highly recommended platform to explore for research purposes. If you are familiar with Web of Science, you will find Scopus user-friendly and worthwhile to explore for comprehensive academic content.

Citation databases can be utilized in combination for more comprehensive research. It is recommended to begin with popular ones like Web of Science and Scopus, as they provide extensive coverage. However, using additional databases can serve as a valuable double-check to ensure no relevant entries are overlooked. Employing multiple databases enhances the likelihood of capturing a comprehensive range of scholarly materials for your research.

While each systematic literature review is unique, there are commonly followed steps that serve as a foundation for the process:

• Clearly define a focused and narrow research question.
• Identify relevant keywords to lead you to articles that can potentially answer your research question.
• Choose a suitable citation database and establish inclusion and exclusion criteria, considering factors like timeframe, discipline, journal, research area, and geographical context.
• Download all pertinent results, which may amount to hundreds of articles.
• Systematically screen all titles and abstracts, manually excluding irrelevant articles based on your criteria.
• Create your own database, such as using Excel, to store the remaining entries and read them more thoroughly.
• Categorize the entries and/or their content in a way that provides meaningful insights to answer your research question.
• Develop visual representations like graphs and tables to present your results.
• Write a concise and engaging presentation of your findings, summarizing the key outcomes of the systematic review.

Following these steps will help you conduct a thorough and well-organized systematic literature review.

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Writing your thesis and conducting a literature review

• Writing your thesis

Your literature review

• Defining a research question
• Choosing where to search
• Search strings
• Limiters and filters
• Developing inclusion/exclusion criteria
• Managing your search results
• Screening, evaluating and recording
• Snowballing and grey literature
• Further information and resources

Most PhD and masters’ theses contain some form of literature review to provide the background for the research.  The literature review is an essential step in the research process. A successful literature review will offer a coherent presentation and analysis of the existing research in your field, demonstrating:

• Your understanding of the subject area
• Gaps in current knowledge (that may in turn influence the direction of your research) 
• Relevant methodologies

There are different approaches and methods to literature reviews, and you may have heard of terms like systematic, structured, scoping or meta-analysis. This is when the literature review becomes the research methodology in its own right, instead of forming part of the research process.

This table shows the differences between a traditional literature review and a structured or systematic literature review.

Traditional vs Systematic literature reviews  

The main types of literature review conducted at cranfield university are defined below..

• Traditional (Narrative)

Positioning Study

Traditional literature review

A traditional literature review or narrative review, is a critical review of the literature on a particular topic, often taking a thematic approach. The aim of this type of literature review is to identify research on your topic, demonstrate your understanding of the research area, and to evaluate the quality and relevance of the literature. You will use your literature review to understand what has already been researched, help develop your research questions and the methodology that you should follow to collect and to identify any areas that your research can explore. You want your research to be unique so you will use a literature review to prevent you duplicating any previous research but also identifying any errors or mistakes that you would want to avoid. A narrative literature review will have uncontrolled bias.  

Structured literature Review

A structured literature review involves bringing many research studies together to use them as the data to determine findings (known as secondary research). There is no other form of data collection involved such as creating your own surveys and questionnaires (primary research). This approach allows you to look beyond one dataset and synthesise the findings of many studies to answer a clearly formulated research question.

Sometimes a structured review may be called a systematic literature review. A structured review typically does not fulfil all the criteria of a full systematic review but may take a similar approach by taking a systematic, step by step method to finding literature. They tend to follow a set protocol for determining the research studies to be included and every stage is documented. The results and conclusions are based on the evidence found, not on the authors own views.

To help you prepare for your structured literature review please complete this interactive workbook .

For Supply chain students 

• To help you prepare for your systematic literature review please complete this interactive workbook .

Before conducting your systematic review, you need to know where your research fits in the literature.  Conducting a positioning study which will help you to identify the breadth, or scope of a topic. It will be broad and help you to map existing literature, identifying key concepts in the research. You will use the positioning study to identify and focus your research topic, becoming a subject matter expert with a strong understanding of the field. A positioning study acts as a precursor to a systematic review.

Systematic literature review

A systematic literature review is a specific research methodology to identify, select, evaluate, and synthesise relevant published and unpublished literature to answer a particular research question. The systematic literature review should be transparent and replicable, you should follow a predetermined set of criteria in your protocol to select studies and help minimise bias. The process will need to be documented throughout. A systematic literature review protocol may be registered, so that others can discover and minimise duplication, and can take several years to complete.

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Doing a Systematic Review: A Student's Guide

Student resources, chapter 1. carrying out a systematic review as a master's thesis.

Explore the wealth of resources available across the web. Here are some good places to start.

Link to the Campbell Collaboration, an organization that prepares, maintains and disseminates systematic reviews in education, crime and justice, social welfare and international development

www.campbellcollaboration.org

Link to the Cochrane Collaboration, an organization that conducts systematic reviews of RCTs of healthcare interventions and diagnostic tests

www.cochrane.org

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What is a Systematic Review?

A simplified process map, how can the library help, publications by hsl librarians, systematic reviews in non-health disciplines, resources for performing systematic reviews.

• Step 1: Complete Pre-Review Tasks
• Step 2: Develop a Protocol
• Step 3: Conduct Literature Searches
• Step 4: Manage Citations
• Step 5: Screen Citations
• Step 6: Assess Quality of Included Studies
• Step 7: Extract Data from Included Studies
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A systematic review is a literature review that gathers all of the available evidence matching pre-specified eligibility criteria to answer a specific research question. It uses explicit, systematic methods, documented in a protocol, to minimize bias , provide reliable findings , and inform decision-making.  ¹  

There are many types of literature reviews.

Before beginning a systematic review, consider whether it is the best type of review for your question, goals, and resources. The table below compares a few different types of reviews to help you decide which is best for you. 

• Scoping Review Guide For more information about scoping reviews, refer to the UNC HSL Scoping Review Guide.

• UNC HSL's Simplified, Step-by-Step Process Map A PDF file of the HSL's Systematic Review Process Map.
• Text-Only: UNC HSL's Systematic Reviews - A Simplified, Step-by-Step Process A text-only PDF file of HSL's Systematic Review Process Map.

The average systematic review takes 1,168 hours to complete. ¹   A librarian can help you speed up the process.

Systematic reviews follow established guidelines and best practices to produce high-quality research. Librarian involvement in systematic reviews is based on two levels. In Tier 1, your research team can consult with the librarian as needed. The librarian will answer questions and give you recommendations for tools to use. In Tier 2, the librarian will be an active member of your research team and co-author on your review. Roles and expectations of librarians vary based on the level of involvement desired. Examples of these differences are outlined in the table below.

• Request a systematic or scoping review consultation

The following are systematic and scoping reviews co-authored by HSL librarians.

Only the most recent 15 results are listed. Click the website link at the bottom of the list to see all reviews co-authored by HSL librarians in PubMed

Researchers conduct systematic reviews in a variety of disciplines.  If your focus is on a topic outside of the health sciences, you may want to also consult the resources below to learn how systematic reviews may vary in your field.  You can also contact a librarian for your discipline with questions.

• EPPI-Centre methods for conducting systematic reviews The EPPI-Centre develops methods and tools for conducting systematic reviews, including reviews for education, public and social policy.

Environmental Topics

• Collaboration for Environmental Evidence (CEE) CEE seeks to promote and deliver evidence syntheses on issues of greatest concern to environmental policy and practice as a public service

Social Sciences

• Siddaway AP, Wood AM, Hedges LV. How to Do a Systematic Review: A Best Practice Guide for Conducting and Reporting Narrative Reviews, Meta-Analyses, and Meta-Syntheses. Annu Rev Psychol. 2019 Jan 4;70:747-770. doi: 10.1146/annurev-psych-010418-102803. A resource for psychology systematic reviews, which also covers qualitative meta-syntheses or meta-ethnographies
• The Campbell Collaboration

Social Work

Software engineering

• Guidelines for Performing Systematic Literature Reviews in Software Engineering The objective of this report is to propose comprehensive guidelines for systematic literature reviews appropriate for software engineering researchers, including PhD students.

Sport, Exercise, & Nutrition

• Application of systematic review methodology to the field of nutrition by Tufts Evidence-based Practice Center Publication Date: 2009
• Systematic Reviews and Meta-Analysis — Open & Free (Open Learning Initiative) The course follows guidelines and standards developed by the Campbell Collaboration, based on empirical evidence about how to produce the most comprehensive and accurate reviews of research

• Systematic Reviews by David Gough, Sandy Oliver & James Thomas Publication Date: 2020

Updating reviews

• Updating systematic reviews by University of Ottawa Evidence-based Practice Center Publication Date: 2007

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Our legacy guide was used June 2020 to August 2022

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• Published: 12 December 2017

Acceptance of a systematic review as a thesis: survey of biomedical doctoral programs in Europe

• Livia Puljak   ORCID: orcid.org/0000-0002-8467-6061 1 , 2 , 3 &
• Damir Sapunar 3  

Systematic Reviews volume  6 , Article number:  253 ( 2017 ) Cite this article

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Systematic reviews (SRs) have been proposed as a type of research methodology that should be acceptable for a graduate research thesis. The aim of this study was to analyse whether PhD theses in European biomedical graduate programs can be partly or entirely based on SRs.

In 2016, we surveyed individuals in charge of European PhD programs from 105 institutions. The survey asked about acceptance of SRs as the partial or entire basis for a PhD thesis, their attitude towards such a model for PhD theses, and their knowledge about SR methodology.

We received responses from 86 individuals running PhD programs in 68 institutions (institutional response rate of 65%). In 47% of the programs, SRs were an acceptable study design for a PhD thesis. However, only 20% of participants expressed a personal opinion that SRs meet the criteria for a PhD thesis. The most common reasons for not accepting SRs as the basis for PhD theses were that SRs are ‘not a result of a PhD candidate’s independent work, but more of a team effort’ and that SRs ‘do not produce enough new knowledge for a dissertation’. The majority of participants were not familiar with basic concepts related to SRs; questions about meta-analyses and the type of plots frequently used in SRs were correctly answered by only one third of the participants.

Conclusions

Raising awareness about the importance of SRs and their methodology could contribute to higher acceptance of SRs as a type of research that forms the basis of a PhD thesis.

Peer Review reports

Systematic reviews (SRs) are a type of secondary research, which refers to the analysis of data that have already been collected through primary research [ 1 ]. Even though SRs are a secondary type of research, a SR needs to start with a clearly defined research question and must follow rigorous research methodology, including definition of the study design a priori, data collection, appraisal of study quality, numerical analyses in the form of meta-analyses and other analyses when relevant and formulation of results and conclusions. Aveyard and Sharp defined SRs as ‘original empirical research’ because they ‘review, evaluate and synthesise all the available primary data, which can be either quantitative or qualitative’ [ 2 ]. Therefore, a SR represents a new research contribution to society and is considered the highest level in the hierarchy of evidence in medicine [ 3 ].

SRs have been proposed as a type of research methodology that should be acceptable as the basis for a graduate research thesis [ 4 , 5 ]. To the best of our knowledge, there are no reports on the acceptance of SRs as the basis for PhD theses. A recent review addressed potential advantages and disadvantages of such a thesis type and presented opposing arguments about the issue [ 5 ]. However, there were no actual data that would indicate how prevalent one opinion is over another with regard to the acceptance of a SR as the primary research methodology for a PhD thesis. The aim of this cross-sectional study was to assess whether a PhD thesis in European biomedical graduate programs can be partly or entirely based on a SR, as well as to explore the attitudes and knowledge of individuals in charge of PhD programs with regard to a thesis of this type.

Participants

The Organization of PhD Education in Biomedicine and Health Sciences in the European System (ORPHEUS) includes 105 institutional members from 40 countries and six associate members from Canada, Georgia, Iran, Kyrgyzstan, Kazakhstan and the USA [ 6 ]. The ORPHEUS encompasses a network of higher education institutions committed to developing and disseminating best practice within PhD training programs in biomedicine, health sciences and public health. ORPHEUS approved the use of their mailing list for the purpose of this study. The mailing list had 1049 contacts. The study authors were not given the mailing list due to data protection and privacy. Instead, it was agreed that ORPHEUS officials would send the survey via email to the mailing list. The General Secretary of the ORPHEUS contacted individuals responsible for PhD programs (directors or deputy directors) among the institutional members, via e-mail, on 5th of July 2016. These individuals were sent an invitation to complete an online survey about SRs as the basis for PhD theses. We invited only individuals responsible for PhD programs (e.g., directors, deputy directors, head of graduate school, vice deans for graduate school or similar). We also asked them to communicate with other individuals in charge of their program to make sure that only one person per PhD program filled out the survey. If there were several PhD programs within one institution, we asked for participation of one senior person per program.

The survey was administered via Survey Monkey (Portland, OR, USA). The survey took 5–10 min to complete. One reminder was sent to the targeted participants 1 month after the first mail.

The ethics committee of the University of Split School of Medicine approved this study, which formed part of the Croatian Science Foundation grant no. IP-2014-09-7672 ‘Professionalism in Health Care’.

Questionnaire

The 20-item questionnaire, designed specifically for this study by both authors (LP and DS), was first tested for face validity and clarity among five individuals in charge of PhD programs. The questionnaire was then modified according to their feedback. The questionnaire included questions about their PhD program; whether PhD candidates are required to publish manuscript(s) before thesis defence; the minimum number of required manuscripts for defending a PhD thesis; the authorship requirements for a PhD candidate with regard to published manuscript(s); whether there is a requirement for a PhD candidate to publish manuscript(s) in journals indexed in certain databases or journals of certain quality, and how the quality is defined; the description about other requirements for defending a PhD thesis; whether a SR partly or fully meets requirements for approval of a PhD thesis in their graduate program; what are the rules related to the use of a SR as the basis for a PhD thesis; and the number of PhD theses based on SRs relative to other types of research methods.

Participants were also asked about their opinion with regard to the main reasons that SRs are not recognised in some institutions as the basis for a doctoral dissertation, and their opinion about literature reviews, using a four-item Likert scale, ranging from ‘agree’ to ‘disagree’, including an option for ‘don’t know’. In the last question, the participants’ knowledge about SR methodology was examined using nine statements; participants had to rate each statement as either ‘correct’, ‘incorrect’, ‘unsure’ or ‘I don’t know’. Finally, participants were invited to leave their email address if they wanted to receive survey results. The survey sent to the study participants can be found in an additional file (Additional file  1 ).

Data analysis

Survey responses were entered into a spreadsheet, checked by both authors and analysed using Microsoft Excel (Microsoft Inc., Redmond, WA, USA). Descriptive data are presented as frequencies and percentages. All raw data and analysed data sets used in the manuscript are available from authors on request. A point-biserial correlation (SPSS, IBM, Chicago, IL, USA) was used to measure the strength of the association between results on the knowledge test (continuous variable) and the attitude towards SRs as the basis for dissertations (dichotomous variable; we used the answer to the following question as this measure: ‘Do you agree that a systematic review, in whole or in part, meets the criteria for a publication on which a doctoral dissertation can be based?’).

Study participants

There are 105 institutions included in the ORPHEUS network. We received a response from 86 individuals representing 68 institutions from 37 countries (65% institutional response rate). There were more respondents than institutions because some institutions have several PhD programs and thus several program directors. Those responders were used as a unit of analysis in the analysis of attitudes and knowledge; institutions were the unit of analysis when analysing criteria for theses. Some of the questionnaires ( n  = 15) were only partly completed. In most cases, the missing data were related to knowledge about SR methodology.

Overview of requirements for a dissertation

Based on the information provided by the graduate program directors, in the majority of the included PhD programs, students were required to publish a research manuscript prepared within their PhD thesis prior to their thesis defence (83%; n  = 64). Among 13 programs (17%) that did not have this requirement, five respondents (38%) indicated that in their opinion their school’s rules related to a PhD thesis should be changed such as to specify that each thesis should be based on work that is already published in a journal.

The minimum number of published manuscripts necessary for the PhD thesis defence was prespecified in 94% ( n  = 60) of the programs that required publication of research manuscripts prior to the thesis defence. In most of the programs (37%; n  = 22), the number of required manuscripts was three or more. Two manuscripts were required in 30% ( n  = 18) and one was required in 33% ( n  = 20) of the programs. In four programs, there was no formal policy on this matter, but there was a strong expectation that the student will have contributed substantially to several manuscripts in peer-reviewed journals.

In most cases, the PhD candidates’ contribution to published manuscripts within the PhD thesis was determined through first authorship. A requirement that a PhD candidate should be the first author on a manuscript(s) that constitutes a PhD thesis was reported in 82% ( n  = 64) of the graduate programs.

In 60% ( n  = 52) of the graduate programs, the quality of the journals where a PhD candidate has to publish research manuscripts as a part of a PhD thesis was defined by the database in which these journals are indexed. The most commonly specified databases were Web of Science (41%; n  = 35) and MEDLINE/PubMed (13%; n  = 11), followed by Science Citation Index, Scopus, Current Contents, a combination of several databases or, in two cases, a combination of journals from a list defined by some governing body.

Systematic reviews as a PhD thesis

SRs, in whole or in part, met the criteria for acceptable research methodology for a PhD thesis in 47% ( n  = 40) of programs, whereas 53% ( n  = 46) of programs specifically stated that they did not accept SRs in this context (Fig.  1 a, b). Among the programs that accepted SRs, theses could be exclusively based on a SR in 42% ( n  = 17) of programs, while in the remaining programs, SRs were acceptable as one publication among others in a dissertation.

a European PhD programs that recognise a systematic review as a PhD thesis (green dot) and those that do not (red dot). Half red and half green dots indicate the five universities with institutions that have opposite rules regarding recognition of a systematic review as a PhD thesis. The pie chart presents b the percentage of the programs in which systematic reviews, in whole or in part, meet the criteria for a dissertation and c the opinion of participants about whether systematic reviews should form the basis of a publication within a PhD dissertation

The majority of participants (80%; n  = 69) indicated that SRs did not meet criteria for a publication on which a PhD dissertation should be based (Fig.  1 c). The main arguments for not recognising a SR as the basis for a PhD thesis are listed in Table  1 . The majority of respondents were neutral regarding the idea that scoping reviews or SRs should replace traditional narrative reviews preceding the results of clinical and basic studies in doctoral theses. Most of the respondents agreed that narrative or critical/discursive literature reviews preceding clinical studies planned as part of a dissertation should be replaced with systematic reviews (Table  2 ).

Most of the programs that accepted SRs as a research methodology acceptable for PhD theses had defined rules related to the use of an SR as part of a PhD thesis (Fig.  2 ). The most common rule was that a SR can be one publication among others within a PhD thesis. Some of the respondents indicated that empty (reviews that did not find a single study that should be included after literature search) or updated reviews could also be used for a PhD thesis (Fig.  2 ).

Frequency of different rules that define the use of systematic reviews as a part of a PhD thesis in European biomedical graduate programs

The results of the survey regarding knowledge about SR methodology indicated that the majority of respondents were not familiar with this methodology. Only three out of nine questions were correctly answered by more than 80% of the participants, and questions about meta-analyses and the type of plots frequently used in a SR were correctly answered by only one third of the participants (Table  3 ). The association between participants’ results on the knowledge test and attitudes towards SRs was tested using a point-biserial correlation; this revealed that lack of knowledge was not correlated with negative attitudes towards SRs ( r pb  = 0.011; P  = 0.94).

In this study conducted among individuals in charge of biomedical graduate programs in Europe, we found that 47% of programs accepted SRs as research methodology that can partly or fully fulfil the criteria for a PhD thesis. However, most of the participants had negative attitudes about such a model for a PhD thesis, and most had insufficient knowledge about the basic aspects of SR methodology. These negative attitudes and lack of knowledge likely contribute to low acceptance of SRs as an acceptable study design to include in a PhD thesis.

A limitation of this study was that we relied on participants’ responses and not on assessments of formal rules of PhD programs. Due to a lack of familiarity with SRs, it is possible that the respondents gave incorrect answers. We believe that this might be the case since we received answers from different programs in the same university, where one person claimed that SRs were accepted in their program, and the other person claimed that they were not accepted in the other program. We had five such cases, so it is possible that institutions within the same university have different rules related to accepted research methodology in graduate PhD programs. This study may not be generalisable to different PhD programs worldwide that were not surveyed. The study is also not generalisable to Europe, as there are no universal criteria or expectations for PhD theses in Europe. Even in the same country, there may be different models and expectations for a PhD in different higher education institutions.

A recent study indicated a number of opposing views and disadvantages related to SRs as research methodology for graduate theses, including lack of knowledge and understanding by potential supervisors, which may prevent them from being mentors and assisting students to complete such a study [ 5 ]. This same manuscript emphasised that there may be constraints if the study is conducted in a resource-limited environment without access to electronic databases, that there may be a very high or very low number of relevant studies that can impact the review process, that methods may not be well developed for certain types of research syntheses and that it may be difficult to publish SRs [ 5 ].

Some individuals believe that a SR is not original research. Indeed, it has been suggested that SRs as ‘secondary research’ are different than ‘primary or original research’, implying that they are inferior and lacking in novelty and methodological rigour as compared to studies that are considered primary research. In 1995, Feinstein suggested that such studies are ‘statistical alchemy for the 21st century’ and that a meta-analysis removes or destructs ‘scientific requirements that have been so carefully developed and established during the 19th and 20th centuries’ [ 7 ]. There is little research about this methodological issue. Meerpohl et al. surveyed journal editors and asked whether they consider SRs to be original studies. The majority of the editors indicated that they do think that SRs are original scientific contributions (71%) and almost all journals (93%) published SRs. That study also highlighted that the definition of original research may be a grey area [ 8 ]. They argued that, in an ideal situation, ‘the research community would accept systematic reviews as a research category of its own, which is defined by methodological criteria, as is the case for other types of research’ [ 8 ]. Biondi-Zoccai et al. pointed out that the main criteria to judge a SR should be its novelty and usefulness, and not whether it is original/primary or secondary research [ 9 ].

In our study, 80% of the participants reported negative attitudes, and more than half of the respondents agreed with a statement that SRs are ‘not a result of the candidate’s independent work since systematic reviews tend to be conducted by a team’. This opinion is surprising since other types of research are also conducted within a team, and single authorship is very rare in publications that are published within a PhD thesis. On the contrary, the mean number of authors of research manuscripts is continuously increasing [ 10 ]. At the very least, the authors of manuscripts within a PhD will include the PhD candidate and a mentor, which is a team in and of itself. Therefore, it is unclear why somebody would consider it a problem that a SR is conducted within a team.

The second most commonly chosen argument against such a thesis was that SRs ‘do not produce enough new knowledge for a dissertation’. The volume of a SR largely depends on the number of included studies and the available data for numerical analyses. Therefore, it is unfair to label a SR as a priori lacking in new knowledge. There are SRs with tens or hundreds of included studies, and some of them not only include meta-analyses, but also network meta-analyses, which are highly sophisticated statistical methods. However, limiting SRs within a thesis only to those with meta-analysis would be unfair because sometimes meta-analysis is not justified due to clinical or statistical heterogeneity [ 11 ] and the presence or absence of a meta-analysis is not an indicator of the quality of a SR. Instead, there are relevant checklists for appraising methodological and reporting quality of a SR [ 12 , 13 ].

The third most commonly chosen argument against SRs within PhD theses was ‘lack of adequate training of candidates in methodology of systematic reviews’. This could refer to either insufficient formal training or insufficient mentoring. The graduate program and the mentor need to ensure that a PhD candidate receives sufficient knowledge to complete the proposed thesis topic. Successful mentoring in academic medicine requires not only commitment and interpersonal skills from both the mentor and mentee, but also a facilitating institutional environment [ 14 ]. This finding could be a result of a lack of capacity and knowledge for conducting SRs in the particular institutions where the survey was conducted, and not general opinion related to learning a research method when conducting a PhD study. Formal training in skills related to SRs and research synthesis methods [ 15 , 16 ], as well as establishing research collaborations with researchers experienced in this methodology, could alleviate this concern.

One third of the participants indicated a ‘lack of appreciation of systematic review methodology among faculty members’ as a reason against such a thesis model. This argument, as well as the prevalent negative attitude towards SRs as PhD theses, perhaps can be traced to a lack of knowledge about SR methodology; however, although the level of knowledge was quite low in our study, there was no statistically significant correlation between knowledge and negative attitudes. Of the nine questions about SR research methodology, only three questions were correctly answered by more than half of the participants. This could be a cause for concern because it has been argued that any health research should begin with a SR of the literature [ 17 ]. It has also been argued that the absence of SRs in the context of research training might severely hamper research trainees and may negatively impact the research conducted [ 18 ]. Thus, it has been recommended that SRs should be included ‘whenever appropriate, as a mandatory part of any PhD program or candidature’ [ 18 ].

It has recently been suggested that the overwhelming majority of investment in research represents an ‘avoidable waste’ [ 19 ]. Research that is not necessary harms both the public and patients, because funds are not invested where they are really necessary, and necessary research may not be conducted [ 17 ]. This is valid not only for clinical trials, but also for other types of animal and human experiments [ 20 ]. SRs can help improve the design of new experiments by relying on current evidence in the field and by helping to clarify which questions still need to be addressed. SRs can be instrumental in improving methodological quality of new experiments, providing evidence-based recommendations for research models, reducing avoidable waste, and enabling evidence-based translational research [ 20 ].

Four respondents from three institutions indicated that empty SRs are accepted as a PhD thesis. While it makes sense to include such a SR as a part of the thesis to indicate lack of evidence in a certain field, it is highly unlikely that an entire thesis can be based on an empty SR, without a single included study.

There are many advantages of a SR as a graduate thesis [ 4 , 5 ], especially as a research methodology suitable for low-resource settings. A PhD candidate can prepare a Cochrane SR as a part of the PhD thesis, yielding a high-impact publication [ 4 ]. Non-Cochrane SRs can also be published in high-impact journals. A PhD candidate involved in producing a SR within a PhD thesis goes through the same research process as those conducting primary research, from setting up a hypothesis and a research question, to development of a protocol, data collection, data analysis and appraisal, and formulation of conclusions. Graduate programs can set limits, such as the prevention of empty reviews and the recognition of updated reviews as valid for a PhD thesis, and engage experienced researchers as advisors and within thesis evaluation committees, to ensure that a candidate will conduct a high-quality SR [ 4 ]. Conducting a SR should not be mandatory, but candidates and mentors willing to produce such research within a graduate program should be allowed to do so.

Further studies in this field could provide better insight into attitudes related to SRs as graduate theses and explore interventions that can be used to change negative attitudes and improve knowledge of SRs among decision-makers in graduate education.

Raising awareness about the importance of SRs in biomedicine, the basic aspects of SR methodology and the status of SRs as original secondary research could contribute to greater acceptance of SRs as potential PhD theses. Our results can be used to create strategies that will enhance acceptance of SRs among graduate education program directors.

Gopalakrishnan S, Ganeshkumar P. Systematic reviews and meta-analysis: understanding the best evidence in primary healthcare. J. Fam. Med Prim Care. 2013;2(1):9–14.

Article   CAS   Google Scholar  

Aveyard H, Sharp P. A beginner’s guide to evidence-based practice in health and social care. Glasgow: McGraw Open Press University; 2011.

Google Scholar  

Cook DJ, Mulrow CD, Haynes RB. Systematic reviews: synthesis of best evidence for clinical decisions. Ann Intern Med. 1997;126(5):376–80.

Article   CAS   PubMed   Google Scholar  

Puljak L, Sambunjak D. Cochrane systematic review as a PhD thesis: an alternative with numerous advantages. Biochemia Medica. 2010;20(3):319–2.

ten Ham-Baloyi W, Jordan P. Systematic review as a research method in post-graduate nursing education. Health SA Gesondheid. 2016;21:120–8.

Article   Google Scholar  

Organisation for PhD Education in Biomedicine and Health Sciences in the European System (ORPHEUS). Available at: http://www.orpheus-med.org/ .

Feinstein AR. Meta-analysis: statistical alchemy for the 21st century. J Clin Epidemiol. 1995;48(1):71–9.

Meerpohl JJ, Herrle F, Reinders S, Antes G, von Elm E. Scientific value of systematic reviews: survey of editors of core clinical journals. PLoS One. 2012;7(5):e35732.

Article   CAS   PubMed   PubMed Central   Google Scholar  

Biondi-Zoccai G, Lotrionte M, Landoni G, Modena MG. The rough guide to systematic reviews and meta-analyses. HSR proc intensive care cardiovascular anesth. 2011;3(3):161–73.

CAS   Google Scholar  

Baethge C. Publish together or perish: the increasing number of authors per article in academic journals is the consequence of a changing scientific culture. Some researchers define authorship quite loosely. Dtsch. Arztebl. Int. 2008;105(20):380–3.

PubMed   PubMed Central   Google Scholar  

Higgins JPT, Thompson SG. Quantifying heterogeneity in a meta-analysis. Statist Med. 2002;21:1539–58.

Liberati A, Altman DG, Tetzlaff J, Mulrow C, Gotzsche PC, Ioannidis JP, Clarke M, Devereaux PJ, Kleijnen J, Moher D. The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration. PLoS Med. 2009;6(7):e1000100.

Article   PubMed   PubMed Central   Google Scholar  

Shea BJ, Grimshaw JM, Wells GA, Boers M, Andersson N, Hamel C, Porter AC, Tugwell P, Moher D, Bouter LM. Development of AMSTAR: a measurement tool to assess the methodological quality of systematic reviews. BMC Med Res Methodol. 2007;7:10.

Sambunjak D, Straus SE, Marusic A. A systematic review of qualitative research on the meaning and characteristics of mentoring in academic medicine. J Gen Intern Med. 2010;25(1):72–8.

Article   PubMed   Google Scholar  

Balajic K, Barac-Latas V, Drenjancevic I, Ostojic M, Fabijanic D, Puljak L. Influence of a vertical subject on research in biomedicine and activities of the Cochrane collaboration branch on medical students’ knowledge and attitudes toward evidence-based medicine. Croat Med J. 2012;53(4):367–73.

Marusic A, Sambunjak D, Jeroncic A, Malicki M, Marusic M. No health research without education for research—experience from an integrated course in undergraduate medical curriculum. Med Teach. 2013;35(7):609.

Mahtani KR. All health researchers should begin their training by preparing at least one systematic review. J R Soc Med. 2016;109(7):264–8.

Olsson C, Ringner A, Borglin G. Including systematic reviews in PhD programmes and candidatures in nursing - ‘Hobson’s choice’? Nurse Educ Pract. 2014;14(2):102–5.

Chalmers I, Glasziou P. Avoidable waste in the production and reporting of research evidence. Lancet. 2009;374(9683):86–9.

de Vries RB, Wever KE, Avey MT, Stephens ML, Sena ES, Leenaars M. The usefulness of systematic reviews of animal experiments for the design of preclinical and clinical studies. ILAR J. 2014;55(3):427–37.

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Acknowledgements

The authors thank the ORPHEUS secretariat for administering the survey and the study participants for taking time to participate in the survey. We are grateful to Prof. Ana Marušić for the critical reading of the manuscript.

This research was funded by the Croatian Science Foundation, grant no. IP-2014-09-7672 ‘Professionalism in Health Care’. The funder had no role in the design of this study or its execution and data interpretation.

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Puljak, L., Sapunar, D. Acceptance of a systematic review as a thesis: survey of biomedical doctoral programs in Europe. Syst Rev 6 , 253 (2017). https://doi.org/10.1186/s13643-017-0653-x

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Food & Function

Effects of a low fodmap diet on the symptom management of patients with irritable bowel syndrome: a systematic umbrella review with the meta-analysis of clinical trials †.

* Corresponding authors

a Department of Clinical Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran

b Colorectal Research Center, Iran University of Medical Sciences, Tehran, Iran

c Yazd Cardiovascular Research Center, Non-communicable Diseases Research Institute, Shahid Sadoughi University of Medical Sciences, Yazd, Iran

d Nutritional Sciences Research Center, Iran University of Medical Sciences, Tehran, Iran E-mail: [email protected] Fax: +98-21-88622533 Tel: +98-21-88622755

e Department of Nutrition, School of Public Health, Iran University of Medical Sciences, Tehran, Iran

f Department of English Language, School of Health Management and Information Sciences, Iran University of Medical Sciences, Tehran, Iran

A low FODMAP diet (LFD) is a common restrictive diet to manage the symptoms of irritable bowel syndrome (IBS). However, there is no consensus on the alleviating effects of this diet. Herein, a systematic umbrella review with meta-analysis was conducted to investigate the effect of an LFD on IBS symptoms and its secondary outcomes in patients, which were not reported in previous meta-analyses. We performed a systematic literature search in PubMed, Scopus, and ISI Web of Science up to December 2023. The methodological quality of systematic reviews and their included trials was evaluated using AMSTAR 2 and the Cochrane risk of bias, respectively. The certainty of the evidence tool was evaluated using the GRADE approach. The data related to IBS symptoms, quality of life (QoL), microbiome diversity, and stool short-chain fatty acids were extracted. A random-effect (if RCTs ≥ 6) or fixed-effect model (if RCTs < 5) was used to recalculate effect sizes and 95% CIs and report them in both qualitative and quantitative terms (pooled risk ratio, Hedges’ g , and weighted mean difference). A total of 658 articles were initially identified, with 11 meta-analyses and 24 RCTs reporting 28 outcomes with 1646 participants included. An LFD significantly affected the clinical improvement of total symptoms according to the IBS-SSS questionnaire (RR: 1.42; 95% CI: 1.02, 1.97; P = 0.04) in all the subtypes of IBS and also had favorable effects on stool consistency (WMD: −0.48; 95% CI: −0.902, −0.07) and frequency (WMD: −0.36; 95% CI: −0.61, −0.10) and some other GI symptoms in both less and more than 4 weeks of diet intervention except for stool consistency, which needed more than 4 weeks of LFD implementation. A significant QoL improvement was observed but not in the anxiety and depression state. Furthermore, some studies showed that an LFD may increase fecal pH and dysbiosis and reduce SCFA and the abundance of Bifidobacterium . In conclusion, an LFD can alleviate symptoms and QoL in IBS patients, although dysbiosis may occur. Considering the low certainty of evidence, strong RCTs with more appropriate designs are needed.

• This article is part of the themed collection: Food & Function Review Articles 2023

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Effects of a low FODMAP diet on the symptom management of patients with irritable bowel syndrome: a systematic umbrella review with the meta-analysis of clinical trials

M. Khalighi Sikaroudi, S. Soltani, S. M. Ghoreishy, Z. Ebrahimi, F. Shidfar and A. Dehnad, Food Funct. , 2024, Advance Article , DOI: 10.1039/D3FO03717G

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