Our study has limitations. It is not currently known whether genetic risk for PTSD differs by trauma type (e.g., combat exposure vs. civilian trauma exposure) or developmental timing (e.g., childhood maltreatment vs. adult assault). Such differences could possibly underlie clinically and biologically important heterogeneity69. Studies of even larger sample size (which MVP will attain in the coming years) and greater granularity with regard to types and chronology of trauma exposure, will be needed to address these questions. It is also important to note that the PCL is a state, not a trait measure, and therefore reflects current – but not necessarily worst-ever lifetime – severity. Our study also reports on the largest African ancestry sample in any PTSD study to date – which we leveraged by inclusion of those individuals in our trans-ancestral meta-analyses – but we relied, out of necessity, on the European ancestry sample for the post-GWAS analyses. We found, as might have been anticipated given prior work70, that PRS derived in the European sample did not predict well into the African sample. Nevertheless, we aspire to using novel tools in the future to make better use of the ancestral diversity in MVP20.
