A longitudinal study of U.S. college students found a small but significant interaction between 5-HTTLPR genotype and past-year stressful life events (SLEs) that accounted for 1.1–3.1% of the variance in frequency of drinking outcomes assessed at two time-points (Covault et al., 2007). Individuals with the SS genotype who experienced multiple past-year SLEs drank more frequently and heavily compared to those with any other combination of genotype and past-year SLEs. There was a similar pattern of GxE for non-prescription drug use. In contrast, among German young adults, those individuals with the LL genotype who experienced early psychosocial adversity had approximately twice as many binge drinking days compared to the LL individuals not exposed to significant early adversity and compared to individuals with LS and SS genotypes regardless of adversity (Laucht et al., 2009). Additionally, current SLEs were associated with greater drinking only among LL and LS individuals.
