Inclusion and exclusion criteria set the boundaries for the systematic review. They are determined after setting the research question usually before the search is conducted, however scoping searches may need to be undertaken to determine appropriate criteria. Many different factors can be used as inclusion or exclusion criteria. Information about the inclusion and exclusion criteria is usually recorded as a paragraph or table within the methods section of the systematic review. It may also be necessary to give the definitions, and source of the definition, used for particular concepts in the research question (e.g. adolescence, depression).
Other inclusion/exclusion criteria can include the sample size, method of sampling or availability of a relevant comparison group in the study. Where a single study is reported across multiple papers the findings from the papers may be merged or only the latest data may be included.