Alcohol consumption is a moderately heritable phenotype, with heritability estimated at approximately 0.5 (Agrawal et al., 2009). Quantitative measures of the heaviness of alcohol consumption have greater power for gene discovery than dichotomous measures of alcohol phenotypes, such as alcohol dependence (AD), as they better represent the underlying continuum of alcohol-related problems. The maximum number of alcoholic drinks consumed in a 24-hour period (MaxDrinks) is a quantitative measure that can be considered an intermediate phenotype or a proxy for AD for gene detection; Diagnostic and Statistical Manual of Mental Disorders (DSM) criterion count is another such measure (Agrawal et al., 2012, Wang et al., 2013, Gelernter et al., 2014, Kendler et al., 2010, Quillen et al., 2014). Although MaxDrinks is highly correlated with alcohol dependence, MaxDrinks is directly associated with alcohol metabolism and physiopathology, which AD is more heterogeneous diagnosis including social functions and legal problems. Genes identified for MaxDrinks may more likely be biologically relevant to alcohol consumption.
