In summary, our analyses illustrate the importance of longitudinal data to characterize how genetic effects unfold across development. This allows us to go beyond simple studies of means and characterize genetic effects on patterns of use across time. By modeling patterns of high risk drinking behavior across time, our analyses suggest that the effect of this gene becomes evident during the transition to young adulthood, as evidenced by a jump in drunkenness evident between age 18 and 19 that is associated with GABRA2 genotype. These findings fit within the broader literature suggesting that environments that exert less social control and/or allow greater opportunity to engage in alcohol use also allow for increased expression of genetic effects (Shanahan and Hofer 2005). Interestingly, our findings are more significant in females. Males overall showed larger increases in drunkenness from 18 to 19 years; accordingly, the effect of genotype was attenuated. This underscores the potential importance of studying how etiological factors may differentially impact alcohol use in males and females at this important developmental juncture. Understanding how genetic risk unfolds across development has important implications for prevention and intervention efforts.
