The sample was composed of 3768 female twins: 964 MZ pairs, 808 dizygotic (DZ) pairs, and 243 singletons from the Missouri Adolescent Female Twin Study (MOAFTS). The MOAFTS is a longitudinal study of alcohol-related problems and associated psychopathology in female adolescents and young adults using twins born in Missouri between 1975 and 1985. Twins were identified through birth records and recruited from 1995 to 1999 using a cohort-sequential design. Cohorts of 13-, 15-, 17- and 19-year-old female twin pairs and their families were ascertained in the first 2 years. New cohorts of 13-year-old twins and their families were added in the subsequent 2 years. Parental diagnostic interviews were completed by at least one parent in 78 % of eligible families. [See Heath et al. (2002) for additional information on ascertainment.] Wave 3 retest interviews were conducted with a subset of Wave 1 participants 2 years after Wave 1 was completed. (Data were not drawn from Wave 2 assessments as they did not cover all domains of interest for this study and referenced experiences from only the previous 24 months.) All
