genetic influences on alcohol dependence is shared with these other disorders, with only ~35% of the heritability being genes that are specific to alcohol dependence (Kendler et al., 2003). These latter, more specific influences are likely to include genes that are involved in alcohol metabolism and related pathways. Genetic variation in several of the alcohol dehydrogenase (ADH) genes, as well as the gene ALDH2 which plays the primary role in converting acetaldehyde to acetate after the metabolism of ethanol to acetaldehyde by the ADH enzymes, have been associated with susceptibility to alcohol dependence (Edenberg et al., 2006; Kuo et al., 2008; Whitfield, 1997). But many of the genes that alter susceptibility to alcohol dependence appear to exert their effects through more non-specific pathways, such as those involved in reward dependence or behavioral disinhibition. Accordingly, they impact a number of different outcomes and contribute to the substantial comorbidity that surrounds alcohol problems.
