The sample was composed of female twins who completed the fourth wave of data collection for the Missouri Adolescent Female Twin Study (MOAFTS), a longitudinal study of alcohol use disorders and related psychopathology in female adolescents and young adults. Female twins born in Missouri to Missouri-resident parents between 1975 and 1985 were identified through birth records and recruited between 1995 and 1999 for the baseline (Wave 1) assessment. Cohorts of 13, 15, 17, and 19 year-old female twin pairs and their families were recruited in the first two years. New cohorts of 13 year-old twins and their families were ascertained in the subsequent two years. Parent interviews were completed by at least one parent in 78% of targeted families. (See Heath et al. (2002) for details on sample ascertainment). Two years after Wave 1 assessments of parents and twins were conducted, Wave 3 retest interviews were administered to a subset of Wave 1 twin participants. (Data from Wave 2 twin interviews were not used in the current study, as they were more limited in scope.) Wave 4 interviews were conducted
