As part of on ongoing study of adult male twins from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders (VATSPSUD) this report is based on data collected from a 2nd and 3rd wave of interviews between 1994 and 2004. The VATSPSUD is described in detail elsewhere (47). Briefly, twins were eligible for participation in this study if one or both twins were successfully matched to birth records, were a member of a multiple birth with at least one male, were Caucasian, and were born between 1940 and 1974. Of 9,417 eligible individuals for the first wave (1993–1996), 6,814 (72.4%) completed the initial interviews. At least one year later, we contacted those who had completed the initial interview to schedule a second interview. The second interview (1994–1998) was completed by 5,629 individuals or 82.6% of those who had completed the 1st interview. The third interview wave (1998–2004), was completed solely by members of male-male twin pairs. Individuals were eligible for this study if they came from a male-male pair, and if both had been interviewed in wave 2.
