This post may seem obvious, but a surprising number of people don't know about Cochrane meta-analyses, so we need more posts like this. We can quote themselves about what they do: What is a systematic review? A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a specific research question. Researchers conducting systematic reviews use explicit, systematic methods that are selected with a view aimed at minimizing bias, to produce more reliable findings to inform decision making.