Cross-sectional and longitudinal studies have found that age at first drink is strongly associated with alcohol-related problem behavior and AUDs (Grant & Dawson, 1997; Pitkanen, Kokko, Lyyra, & Pulkkinen, 2008). The association may be partially accounted for by non-familial factors (Buchmann et al., 2009; Grant et al., 2006) as well as due to overlapping risk for early alcohol consumption and AUDs (McGue, Iacono, Legrand & Elkins, 2001; Prescott & Kendler, 1999). Early alcohol consumption could also interact with genetic liability, potentiating AUD risk among individuals exposed to alcohol at an early age. Using data from a sample of Australian adult twins, Agrawal and colleagues (2009) found that self-reported age at first drink moderated estimates of genetic influences on number of lifetime AD symptoms. Among early drinkers, variation in AD symptoms was predominantly attributable to genetic influences (e.g., approximately 70% for onset by age 14), whereas for those with later drinking onset, variation in AD symptoms was decreasingly attributable to genetic influences (e.g., approximately 45% and 15%, respectively, for onset ages of 16 and 19).
