Alcohol use phenotypes are genetically influenced, with heritability for alcohol use disorder typically estimated at around 50% in twin and adoption studies (Heath et al., 1997; McGue, 1999; Prescott and Kendler, 1999; Verhulst et al., 2015). Other alcohol-related phenotypes, such as initiation of use, typical consumption, maximum number of drinks consumed in a day, or initial response to alcohol, are also modestly to moderately heritable (Fowler et al., 2007; Poelen et al., 2009; Agrawal et al., 2011; Kalu et al., 2012). As these measures constitute steps along the trajectory to alcohol problems among some individuals, elucidating their genetic etiology is important.
