Hi James

In a sense, the number of studies you end up synthesizing/analyzing/summarizing is your sample size. Increasing sample size (from zero) rapidly adds to your information, until at some point the curve starts to bend (diminishing returns as n increases). So the added information value of a second study compared to the first is much larger than the added value of the 100th compared to the 99th.

I am unaware of a minimum number of papers required but I'm not sure this is the way to approach the review.

I think the most important issues are the comprehensiveness of your search strategy, and the approach you use to critically appraise each study for risk of bias. If you can rank your studies in terms of risk of bias, you can then systematically compare the results across strata (to see if the 'good' studies come to different conclusions than the 'not as good' studies). Having knowledgeable independent reviewers with high inter-rater reliability is important.

So if in the end you have a 'small' number of studies that all have an acceptably low risk of bias, you can be more confident of the summary conclusions than with a larger number of studies many of which have a high risk of bias.

In my view, usually, the number of records for SR depends on your inclusion criteria and PRISMA Flow chart

https://guides.lib.unc.edu/prisma

I agree with the previous replies. Without reading them I would have had a simpler answer: the right number is: All relevant studies.

If you'd stop after reaching some number, then you are not doing a systematic review.

Considero que el numero de revisiones depende de la sistematicidad, rigurosidad y relevancia de la revisión. Situación que depende del investigador y de su intencionalidad con la investigación

Number of articles will purely depend on you inclusion and exclusion criteria. there is no number considered good, but search should be comprehensive and strict criteria should be mentioned for inclusion

There should be no minimum number. It depends on how many relevant documents exist on the subject. However an editor asked me to consider at least 100 documents

The number of articles included in the final review can vary from hundreds to a handful. The most important part of a systematic review is the PICO question - Population, Intervention, Comparison, and Outcome. Based on the question that the review is trying to answer, you can formulate your inclusion and exclusion criteria. However, it is the search strategy, the MESH terms, and combination of terms, the search engines included, pubmed, cochrane, etc. which account for much more than the number of studies included in the final review. Hope this is helpful. I have included a couple systematic reviews from our group which you can use to identify the search strategy, formulating your question, as well as the inclusion and exclusion criteria.

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