Is risk for alcoholism mediated by individual differences in drinking motivations?

BACKGROUND: Individual differences in motivations to drink have been proposed as a mechanism that mediates risk for alcoholism. We investigated the genetic and environmental sources of variation in motivations for drinking, as assessed by four scales of the Alcohol Use Inventory (AUI), and then examined the extent to which genetic and environmental variations in risk for alcoholism are mediated by individual differences in drinking motives.
METHODS: Data on four AUI scales (assessing drinking to manage mood states, to relieve social anxiety, in social situations, and to improve mental functioning) and lifetime DSM-IV alcohol abuse and/or dependence (AAD) were obtained from 2529 female and 3709 male adult twins, including 2229 complete twin pairs, from the population-based Virginia Twin Registry.
RESULTS: Logistic regression analyses indicated that higher scores on each of the four AUI variables were significantly associated with AAD, with increases in risk for diagnosis of 40% to 141% per standard deviation increase in AUI score. Structural modeling analyses conducted using Mplus indicated that individual differences in AUI scores were in part due to genetic variation, particularly among women. Among males, genetic factors were substantial for drinking to alter mood but small for other measures. A substantial portion of the genetic variation in AAD overlapped with drinking to manage mood states. Results from bivariate twin models of AAD and the AUI scales were consistent with the mediation hypothesis for the social anxiety and social interaction scales but not drinking to manage mood or to enhance mental functioning.
CONCLUSIONS: Genetic contributions to variation in risk for alcoholism may be mediated in part by individual differences in motivations related to drinking in social settings. Drinking to manage mood indexes genetic risk for alcoholism but does not appear to act as a direct cause of alcoholism.