Participants were from the Minnesota Twin Family Study (MTFS), an ongoing longitudinal study of a community-based sample of same-sex twins born in the state of Minnesota and their parents (Iacono & McGue, 2002). Participants were originally identified from public birth records and contacted over the phone or by mail. Families were eligible to participate if they lived within a day’s drive of our labs and if neither twin had a cognitive or physical handicap that precluded participation. Written informed assent or consent was collected from each participant and their parents or guardian. This study focuses on the younger cohort of twins from the MTFS born between 1977 and 1985 and first assessed between the ages of 10 and 12 years. Almost all participants were Caucasian (98%), consistent with the demographics of Minnesota at the time that this study began. Data from this report comes from the younger cohort’s third assessment (ages: males: M =18.04, SD= 0.66; females: M=18.28, SD = 0.71) as a comprehensive alcohol use assessment was conducted with this cohort for the first time. Our aim was to
