but found evidence for an association with CD in adolescents (Dick et al. 2006; Sakai et al. 2010). These results are not altogether surprising since estimates of heritability of alcohol dependence are roughly 64% in adulthood (Heath et al. 1997), yet no genetic effects are present in adolescence, with variance in adolescent alcohol dependence being attributed to environmental influences (Rose et al. 2004). It is worth noting however, that a recent longitudinal study showed genetic influences ranging from 35-40% on general substance use disorders between ages 14-17 that decreased with age (Vrieze et al. 2012).
