Many alcohol related phenotypes are heritable in both adolescents and adults (Heath et al. 1991; Heath et al. 1997; Heath and Martin 1994; Hopfer et al. 2005; Kendler et al. 1994; Pagan et al. 2006; Rhee et al. 2003). However, the heritability of these phenotypes is contextually dependent on a number of social factors. For adolescents, a study of adolescent lifetime alcohol use reported a heritability of 72%, but only in those who did not have parental permission to drink (Maes et al. 1999). In adolescents who had parental permission to drink, genes were not a salient contributor to the variance of lifetime alcohol use. Similarly, genetic risk for drinking frequency was found to be more salient in twins from urban (vs. rural) backgrounds (Rose et al. 2001) and twins whose peers use drugs (Dick et al. 2007); the heritability of male drinking patterns was higher in those whose parent were frequent drinkers than in those from non/low drinking households (Cleveland and Wiebe 2003). Moreover, heritability of intoxication frequency was found to be more heritable in independent twins than in
