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Systematic Reviews & Other Syntheses

MEDLINE: Did you know?

You can search MEDLINE using PubMed or the Ovid interface. PubMed is a free resource that you will always be able to access, whereas Ovid MEDLINE is a proprietary resource that has been purchased by Queen's University Library. The Ovid interface and may be more user-friendly for new searchers than PubMed and provides a consistent look and feel if searchers will be accessing other databases on the Ovid platform such as Embase, Cochrane CENTRAL, PsycINFO, Global Health, and AMED.

Cochrane: Did you know?

The library provides access to two different interfaces for searching Cochrane Library: Wiley or Ovid. If your review will only be synthesizing primary studies, there is no need to search all of Cochrane Library (which also includes the Database of Systematic Reviews), instead, limit your search to Cochrane CENTRAL to retrieve trials only.


Deciding where to search for studies will largely depend on the review type and topic. A comprehensive search approach is often the goal, as systematic reviews and some other syntheses attempt to identify all evidence for a given research question. Locating studies for syntheses often includes searching for both published and unpublished ("grey") literature.

Studies for your syntheses may be found in the form of:

  • peer-reviewed journal articles
  • preprint articles
  • conference abstracts/papers
  • dissertations and theses
  • governmental or private sector research
  • ongoing or unpublished clinical trials

Library Databases

Bibliographic/citation databases contain bibliographic information (e.g., citation information and abstracts) for sources of literature. The databases compared and listed below predominantly include bibliographic records of journal articles, but some also contain records for conference abstracts/papers, preprints, dissertations, and more. 

Queen's University Library provides access to broad coverage databases in the health sciences (such as Ovid MEDLINE and Embase) as well as smaller subject-specific databases (such as PsycINFO and CINAHL). See the Database Comparison further down this page to learn more about some of these databases. 

Directly below is a list of the most popular health sciences databases that Queen's has access to. It is not a comprehensive list of potentially relevant databases. Depending on your review topic, it may also be appropriate to search in databases from other disciplines such as the social sciences, law or education. To discover more databases that might be relevant for your topic, try the Browse Databases by Subject feature on the library website or speak with a librarian.

Database Comparison






Cochrane Library

Web of

BIOSIS Previews






Varies by database





> 8,500







> 33 million

> 41 million

~4 million

> 5 million

>1 million

>171 million

 > 18 million

 Record   Types:

Mainly journal articles 

Journal articles, conference abstracts/papers, preprints

Journal and magazine articles, dissertations, books

Journal articles, book chapters, dissertations

High-quality controlled trials and systematic reviews

Journal articles, book chapters, conference proceedings

Journal articles, book chapters, conference proceedings, patents
Biomedicine incl. 
allied health, biological and physical sciences and humanities
 pharmacology, toxicology,
life sciences, and healthcare admin
Nursing, biomedicine, allied health and alternative medicine Psychological literature incl. social, behavioral, and health sciences Evidence for healthcare interventions and diagnostic assessment  Multidisciplinary incl. science, technology, education, humanities & social sci  Life sciences: biotechnology, neuroscience, pharmacology,  toxicology, and zoology 





APA Thesaurus Terms

MeSH, but only for some records




Ovid and PubMed



Ovid and

Ovid and

Web of

Web of


No need to search both Ovid MEDLINE and PubMed

Aka Ovid EBM Reviews





Hand-searching relevant journals page by page can be incredibly time-consuming but it may identify additional studies that have been missed by database search strategies or studies from journals that are not covered in electronic databases.

Research evidence:

  • A systematic review by Hopewell et al. (2007) on the efficacy of handsearching to identify reports of randomized trials found that "...a combination of handsearching and electronic searching is the most comprehensive approach in identifying reports of randomized trials" (p. 2). However, the authors noted "...where time and resources are limited, searching an electronic database using a complex search will identify the majority of trials published as full reports in English language journals, provided, of course, that the relevant journals have been indexed in the database" (p. 2).

Conference proceedings

Databases may not index conference proceedings, and even if they do, coverage may be limited. Hand-searching relevant conference proceedings that are available on association or conference websites may identify additional relevant studies.

Searching Reference Lists

Once you have identified eligible studies for your knowledge synthesis by searching the appropriate resources above, it is best practice to then check the reference lists of these studies to identify any additional studies. The reference lists of related reviews may also help to identify additional studies.

Research evidence:

  • A systematic review was conducted by Horsley et al. (2011) to determine whether searching reference lists actually identifies additional studies during the systematic review process. Most studies included in their systematic review reported that this practice did identify additional studies; however, the evidence supporting this practice most often came from case report data and not high quality research. Despite this, Horsley et al. still recommend that systematic reviewers screen the reference lists of relevant studies to find additional studies, especially when you're struggling to find relevant information.

Cited Reference Searching

Citation indexes such as Web of Science (or the search engine Google Scholar) can be used for cited reference searching. Citation reference searching allows you to identify where eligible studies have later been cited to see if this identifies any additional studies.

For example, if you search for a relevant study in Google Scholar you will see a "Cited by..." link underneath the study information that indicates how many times the study has been cited (unless the study has not yet been cited). You can follow this link to view where the study has been cited to see if this locates any additional studies.


Cooper, C., Lovell, R., Husk, K., Booth, A., & Garside, R. (2017). Supplementary search methods were more effective and offered better value than bibliographic database searching: a case study from public health and environmental enhancement. Research Synthesis Methods, (October 2017), 195–223. 
Craven, J. and P. Levay (2019). Systematic Searching: Practical Ideas for Improving Results, Facet Publishing.

Hartling, L., Featherstone, R., Nuspl, M., Shave, K., Dryden, D. M., & Vandermeer, B. (2016). The contribution of databases to the results of systematic reviews: a cross-sectional study. BMC Medical Research Methodology, 16.
Hopewell, S., Clarke, M., Lefebvre, C., & Scherer, R. (2007). Handsearching versus electronic searching to identify reports of randomized trialsCochrane Database of Systematic Reviews2.

Horsley, T., Dingwall, O., & Sampson, M. (2011). Checking reference lists to find additional studies for systematic reviewsCochrane Database of Systematic Reviews, 10(8).

Lefebvre C., Glanville J., Briscoe S., Littlewood A., Marshall C., Metzendorf M.-I., Noel-Storr A., Rader T., Shokraneh F., Thomas J. & Wieland L.S. Chapter 4: Searching for and selecting studies. In: Higgins J.P.T., Thomas J., Chandler J., Cumpston M., Li T., Page M.J. & Welch V.A. (Eds). Cochrane Handbook for Systematic Reviews of Interventions version 6.0 (updated July 2019). Cochrane, 2019. Available from

Lefebvre, C., Glanville, J., Wieland, L. S., Coles, B., & Weightman, A. L. (2013). Methodological developments in searching for studies for systematic reviews: past, present and future? Syst Rev, 2(1), 78. 

McAuley, L., Pham, B., Tugwell, P., & Moher, D. (2000). Does the inclusion of grey literature influence estimates of intervention effectiveness reported in meta-analyses? The Lancet, 356(9237), 1228–1231. 

Papaioannou, D., Sutton, A., Carroll, C., Booth, A., & Wong, R. (2009). Literature searching for social science systematic reviews: consideration of a range of search techniques. Health Information & Libraries Journal, 27(2), 114–122.

Schmucker, C. M., Blümle, A., Schell, L. K., Schwarzer, G., Oeller, P., Cabrera, L., … Consortium,  on behalf of the O. (2017). Systematic review finds that study data not published in full text articles have unclear impact on meta-analyses results in medical research. PLOS ONE, 12(4).

Stansfield, C., Dickson, K., & Bangpan, M. (2016). Exploring issues in the conduct of website searching and other online sources for systematic reviews: how can we be systematic? Systematic Reviews, 5(1).