Studies with data sharing restrictions followed similar criteria for quality control, as detailed in Supplementary Table 28 and in the references in the supplemental material. Studies were imputed to either the 1000G phase 3, HRC, SISu panel, or a composite panel. GWAS summary data were lifted to the GRCh37 reference build where required. As differences in the imputation panels and genome reference build can result in SNP-level discrepancies between datasets, each set of summary data was examined for correspondence to the centrally imputed data. Multi-allelic SNPs and SNPs with non-matching allele codes were excluded. Strand ambiguous SNPs with high MAF difference (>20%) from the average frequency calculated in the PGC-PTSD data were flagged and examined for strand correspondence.
