Alcohol dependence (alcoholism) is a complex disorder with a 40–60% genetic contribution to risk (Edenberg & Foroud, 2006; Heath et al., 1997; McGue, 1999). Although several genes in which variants affect the risk for alcohol dependence have been identified (Rietschel & Treutlein, 2012), their overall effect accounts for only a small portion of the vulnerability to alcohol dependence. Many studies are underpowered, and determining which modest association results are true positives can be difficult. Studies of gene expression in the human brain can reveal differences between alcoholics and controls that might be either risk factors or sequelae of excessive drinking; in either case, this increases the likelihood that such genes are relevant to the disease.
