Alcohol drinking behavior can be measured in a number of ways, including cross-sectional measures of alcohol consumption (e.g. drinks per week), and lifetime measures (e.g. alcohol dependence). There is strong evidence that individual variation in each of these measures is determined by both genetic and environmental factors, and there is strong, if incomplete genetic correlation among them.20, 21 Genetic epidemiologic studies, such as twin and family/adoption studies, have estimated that about half of the variance in these traits may be explained by genetic factors.20, 22, 23 Genetic association studies have demonstrated a pharmacogenetic effect of missense variants in genes in the alcohol metabolism pathway, specifically, alcohol dehydrogenase 1B (ADH1B) and aldehyde dehydrogenase 2 (ALDH2), that influence lifetime measures, such as risk of alcohol dependence.24, 25 While these variants play an important role in determining individual levels of alcohol use, they explain a small proportion of the genetic contribution to variation in alcohol use reported in twin studies. Recently, genome-wide association studies (GWAS) of alcohol consumption have identified potential novel susceptibility loci, however, only a few have been confirmed in independent
