Selected results were confirmed, and heterogeneity statistics were calculated, using Comprehensive Meta-analysis version 2.0. This performs a random-effects meta-analysis that is robust to sample heterogeneity, as well as explicit tests of heterogeneity using Q and I statistics.23 In order to account for overlap in control samples, we grouped cases from the NIMH-BP and STEP-BD samples (which do not overlap), and compared them, as a whole, with the controls used in the STEP-BD report, as recommended by some authorities24,25.
