The current report is based on data collected in wave 3 of structured clinical interviews with adult Caucasian male twins participating in the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders (VATSPSUD, Kendler & Prescott, 2006). Participants were originally ascertained from the population-based Virginia Twin Registry, were born between 1940 and 1974, and were 24–62 years old (mean=40.3, SD=9.0) at the time of their interview. Much of the sample (39%) had completed an associate’s degree or higher; 24% attended vocational school or some college; 29% had a high school diploma or GED; and 8% did not complete high school. Most were married (65%) or cohabitating (4%); 12% were divorced/separated/widowed. Informed consent was obtained after an explanation of the research protocol was provided; the Institutional Review Board at Virginia Commonwealth University approved the project. Interviews were conducted face-to-face or over the phone by trained interviewers. Zygosity was determined using a combination of self-report measures, photographs, and genotyping. In the current study, partial or complete data were available for N=1790 individuals (including 466 complete monozygotic [MZ] and 283 complete dizygotic [DZ] twin pairs).
