Previous research has indicated that the Vietnam Era Twin Registry is generally representative of twins who served in the military during the Vietnam-era (Goldberg et al., 1987; Henderson et al., 1990). Goldberg et al. (1987) reported differences in date of enlistment/discharge, duration of service, branch of service, and service in Southeast Asia between individuals included in the Defense Manpower Data Center database (the source of the Registry) and the State of Connecticut twin register (for which a manual search of hard copy military records was conducted). When examining attrition from the full Registry to the SOH, Henderson et al. (1990) found that SOH non-responders were more likely to be non-White, had lower education at enlistment, were younger at enlistment, and were less likely to have served in Southeast Asia.
