The Missouri Adolescent Female Twin Study (MOAFTS) is a longitudinal study of substance use and related psychopathology in adolescent girls and young women, conducted with same-sex female twins born in Missouri to Missouri-resident parents between July 1, 1975 and June 30, 1985. Twins were identified through birth records and recruited for baseline assessment from 1995 to 1999. The sample was demographically representative of the Missouri population at the time the twins were born, with nearly 15% being AA and the remainder EA (see Heath et al., 1999, 2002; Waldron et al., 2013 for details). Wave 1 interviews were conducted with 3,258 twins (median age=15). Many but not all twin pairs from Wave 1 completed a brief 1-year follow-up (Wave 2, not a source of data for the current study), and a subsample from Wave 1 also completed a comprehensive 3-year retest interview (Wave 3, n=1,370, median age=19). Between 2002 and 2005, all twins from the target cohort (excluding those who had withdrawn or whose parents asked that the family not be re-contacted) were contacted for Wave 4 interviews (n=3,787, median
