This study assesses the longitudinal, developmental trajectory of risk associated with a specific genotype in a large prospective cohort of adolescents with drinking patterns characterized from adolescence to young adulthood. Understanding risk across this period is a particularly critical area of study in the alcohol field, as there has been a discrepancy between genetic findings for alcohol related outcomes in adolescent and adult samples (Dick, Bierut et al. 2006; Sakai, Stallings et al. 2010). With longitudinal data we demonstrate that genotype effects are associated with the transition to adulthood: genetic differences emerge as a jump in drunkenness between age 18 and 19. This is obviously a rich developmental phase that is associated with a number of milestones, such as leaving home, entering college, and building new social networks (White, Xie et al. 2001; Borsari, Murphy et al. 2007). These milestones reflect enhanced independence associated with the attainment of adult status. Twin data have indicated that environments that exert less social control and/or provide greater opportunity to engage in alcohol use allow for greater expression of genetic predispositions (Dick and Kendler
