the SSAGA; participants who reported a qualifying trauma were then queried about symptoms of PTSD that were required for a DSM-IV diagnosis (Diagnostic and Statistical Manual of Mental Disorders-IV) [35, 37]. For the purpose of this study, data were included only for COGA participants that were assessed for trauma exposure and/or PTSD. Of the 17,854 COGA participants, 8878 were assessed for lifetime DSM-IV PTSD diagnosis. Because exposure to trauma is needed for a PTSD diagnosis, and to remain consistent with published GWAS, the analytic sample for our study was limited to the 4978 out of 8878 (56%) participants assessed for DSM-IV PTSD (AA N = 1468; EA N = 3510) who were both genotyped and reported experiencing a DSM-based qualifying traumatic event. This was done so as to not conflate genetic influences on trauma exposure and genetic influences on PTSD. Although the statistical power is relatively limited, especially for the AA sample, we conducted this analysis to emphasize the importance of including underrepresented populations in genetic studies. Descriptive statistics for the GWAS analytic sample are displayed in Supplemental Table 1.
