We created an externalizing behavior/disorder composite measure based on both non-clinical and clinical indicators measured in the first follow-up (when offspring were, on average, aged 15) C-SSAGA interview, which has demonstrated reliability and validity (Bucholz et al., 1994; Hesselbrock et al., 1999): (1) alcohol use, (2) marijuana use, (3) cigarette use, (4) DSM-IV clinical criterion counts (American Psychiatric Association, 1994) of conduct disorder (CD) criteria, and (5) DSM-IV oppositional defiant disorder (ODD criterion counts). Rather than using the more severe clinical-level substance use problems as sole indices of the externalizing behaviors, we used developmentally-appropriate substance use variables to capture more variability in externalizing behavior in our sample of young adolescents. Alcohol use was measured in the C-SSAGA by asking individuals to rate the frequency of past-year drinking on a 12-point scale from 1 (about 1 to 2 days a year) to 12 (every day). Non-drinkers were coded as zero. Marijuana use was assessed by asking participants to report the number of times they used marijuana in the last 12 months. Cigarette use was coded as 1 = past-year use, and
