Enrollment involves providing a blood sample for genomic analyses, allowing ongoing access to medical records and other administrative health data by authorized MVP staff, and completing questionnaires. Two surveys are provided to MVP participants: the MVP Baseline Survey, for demographic factors, family pedigree, health status, lifestyle habits, military experiences, medical history, family history of specific illnesses, and physical features; and the optional MVP Lifestyle Survey, which includes the PCL (DSM-IV version)33. This PCL version resembles the civilian version (PCL-C) in that it asks respondents to report how much they have been bothered in the past 30 days by symptoms in response to “stressful experiences” (i.e., not just military experiences). We scrutinized the symptom cluster most distinctive for PTSD, re-experiencing (REX) symptoms (range 5–25). REX items and their distributions in EAs and AAs are shown in Table S1 and Figure S1. Chronbach’s alpha for REX was calculated with the alpha function in the psych R package to test the internal consistency of the 5 items which make up the re-experiencing cluster. Chronbach’s alpha for the 5 reexperiencing items was 0.94 in
