Cochrane Overviews use different methods from Cochrane Intervention reviews; they summarize existing Intervention reviews rather than find and summarize or synthesize original studies. Key differences in methods between Cochrane Intervention reviews and Cochrane Overviews are summarized in Table 22.2.a.
Cochrane Overviews of reviews do not aim to repeat the searches, assessment of eligibility, assessment of risk of bias or meta-analyses from the included Intervention reviews. In addition, they do not typically aim to identify systematically any additional studies or to extract additional outcomes from studies. They do include assessment of limitations of included systematic reviews, and may include meta-analyses across reviews to provide indirect comparisons of the effects of different interventions on a given outcome. This is not to imply that overviews of systematic reviews that undertake a more detailed analysis including critical appraisal, new searches and new analyses are inappropriate, but they are not what is envisaged for Cochrane Overviews.