Effective sample size-weighted meta-analyses across case-control and family-based samples within ancestry were done using METAL (appendix pp 13–14).23 First, summary statistics of case-control and family-based samples from the Psychiatric Genomics Consortium were combined and weighted by the effective sample size, because effect sizes from case-control logistic regression analyses and family-based analyses using generalised estimating equations and logistic mixed models are not directly comparable. Then the Psychiatric Genomics Consortium results were meta-analysed with those from the iPSYCH and deCODE samples (between-sample genetic correlations [rg] 0·66–0·70). The summary statistics were filtered such that an SNP had to be present in at least two of the three contributing GWASs (deCODE, iPSYCH, and the Psychiatric Genomics Consortium).
