The hazardous and harmful use of alcohol is a major contributing factor to death, disease and injury globally. Almost 4% of all deaths worldwide are due to alcohol, more than the percent of deaths caused by HIV/AIDS, violence or tuberculosis (World Health Organization, 2011). Both genetic and environmental factors influence the initiation of alcohol use and subsequent alcohol dependence (AD; Bierut, 2011; Kendler et al., 2008; Wang et al., 2012). AD is a complex disorder with high heritability (50-60%; Heath et al., 1997; Kendler et al., 2010, 1994). However, the relationship between genetic risk factors and AD is likely complex, due to the interplay between genes and the environment (Blomeyer et al., 2013; Perry et al., 2013; van der Zwaluw and Engels, 2009).
