Lifetime presence of DSM-III-R (American Psychiatric Association, 1987) disorders, the diagnostic system in place at the time the present cohort of participants were assessed, was determined via in-person, structured interviews by trained clinical interviewers. Symptoms of nicotine dependence, alcohol dependence, and illicit drug dependence were assessed using an expanded version of the Substance Abuse Module of the Composite International Diagnostic Interview (Robins, Babor, & Cottler, 1987). An interview designed by MTFS staff (Holdcraft, Iacono, & McGue, 1998) was used to assess symptoms of conduct disorder and adult antisocial behavior (i.e., the adult criteria for Antisocial Personality Disorder). Mothers of the twins reported on the substance use and childhood antisocial behaviors of each twin through interviews using the parent version of the Diagnostic Interview for Children and Adolescents (Reich, 2000). Symptoms were assigned on the basis of a consensus, “best-estimate” approach (Leckman, Scholomskas, Thompson, Belanger, & Weisman, 1982) combining mother and twin interview data.
