The VA sample was comprised of U.S. military veterans and a subset of their intimate partners (N=852) who were enrolled in one of two studies conducted at two U.S. Department of Veterans Affairs (VA) Healthcare facilities. Both studies were reviewed and approved by the appropriate human subjects and local institutional review boards. Data were not analyzed for 42 cases who did not complete the protocol, 25 cases who enrolled in both studies (in which case, only data from the first study was included) and DNA was not available for 24 participants due to problems with the blood draw. This yielded a subsample of (n=761) with complete data, of whom 729 had been exposed to a traumatic event meeting the DSM-IV PTSD Criterion A definition as determined by a clinician using the Clinician-Administered PTSD Scale (CAPS9 (link)). Of these events, the most common type was combat trauma, endorsed by 33.6% of the sample (54.7% of men; 2.4% of women). The trauma-exposed subsample was predominantly male (n=435, 59.7%) with a mean age of 51.5 (SD=10.9). 496 (68%) were veterans and the remaining 233 were their spouses or intimate partners. 409 participants (53.7%) met criteria for a lifetime diagnosis of PTSD based on the CAPS.
Ancestry was determined using 10,000 randomly chosen markers with MAF>.05 by the program STRUCTURE 10 (link), 11 (link) which performs a Bayesian clustering analysis to assign subjects to ancestry groups (see additional details below). From this analysis, 491 individuals with a history of trauma exposure and valid genotype data were identified as having primarily white non-Hispanic ancestry, 84 were identified as having African American ancestry, and 105 were of “other” ancestry (including individuals self-described as having Hispanic, Native American, or Asian ancestry). We found no evidence of PTSD-associated population substructure within the VA-sample ancestry groups (see supplementary materials for details).