For decades, the systematic review of published randomised controlled trials has been considered the gold standard in medical research, and this was what the original Cochrane reviewers did.
By combining data from all published trials on a particular subject, researchers are able to see effects in much larger numbers of people than would typically be included in a single trial, in theory making their conclusions more powerful.
In theory. The problem in reality is a small thing called publication bias.
Some trials are simply more likely to be published than others, potentially skewing the results of this kind of meta-analysis.
MJA InSIght, Monday, 14 October, 2013
