That genetic factors have an age-specific influence on the onset of alcohol dependence is suggested by the findings that there are strong genetic effects contributing to risk for alcohol dependence particularly connected with early onset of drinking activity (Rangaswamy and Porjesz, 2008; Sartor et al., 2009; Agrawal et al., 2009; Xuei et al., 2010; Kendler et al., 2011; Lee et al., 2012). Correspondingly, the rate of adult alcohol dependence is significantly greater among those who start drinking at a relatively early age (14 years or younger) than among those who start drinking after the age of 19 (Grant and Dawson, 1997) (see also Hingson et al. (2006a, b); Hussong et al. (2008); Chen et al. (2011)).
