A robust body of research using genetically-informative twin data demonstrates that genetic influences on alcohol use vary across development. Heritability changes across development; for instance, previous studies have found that the heritability of alcohol use increases from adolescence to emerging adulthood (Huibregtse et al. 2016; Kendler et al. 2008; Rose et al. 2001; Viken et al. 1999). This increase in heritability over time is partly driven by “genetic innovation”, which refers to new genetic risk factors that emerge throughout development (Edwards & Kendler, 2013; Long et al. 2017). Simultaneously, other genetic risk factors may become less important at later ages. Different genetic variants influence alcohol use at different developmental periods. Twin studies indicate that alcohol-specific and broader externalizing genetic factors operate at different developmental stages (Kendler et al. 2011; Meyers et al. 2014). The environment plays an important role in shaping these differences throughout development; for example, alcohol use in adolescence requires illicit access to alcohol. Relatedly, broad externalizing genetic factors are particularly salient in adolescent alcohol use (Kendler et al. 2011; Meyers et al. 2014).
