At the age-11 and age-14 assessments, participants were assessed for DSM-III-R (12) nicotine dependence, alcohol dependence/abuse, and marijuana dependence/abuse using the Diagnostic Interview for Children and Adolescents (DICA-R; (13)). All later assessments used a modified version of the Substance Abuse Module (SAM; (14)) of the Composite International Diagnostic Interview (CIDI; (15)) to assess DSM-III-R symptoms of substance use disorders. Abuse and dependence symptoms were collapsed for alcohol and marijuana. Mother reports of their children’s symptoms were also obtained at ages 11, 14, and 17. The follow-up assessments at each age covered the interval elapsing since the last assessment. A “best -estimate” approach (16) was used whereby a symptom was considered present if reported by either the child or mother. Diagnostic inter-rater reliability of substance use disorders was greater than .91 (17). To rule out possible informant effects, all analyses were repeated using only the child as the informant. The pattern of results was identical.
