Socioeconomic status moderates genetic and environmental effects on the amount of alcohol use.

BACKGROUND Much is unknown about the relationship between socioeconomic status (SES) and alcohol use, including the means by which SES may influence risk for alcohol use. METHODS Using a sample of 672 twin pairs (aged 25 to 74) derived from the MacArthur Foundation Survey of Midlife Development in the United States, this study examined whether SES, measured by household income and educational attainment, moderates genetic and environmental influences on 3 indices of alcohol use: amount used, frequency of use, and problem use. RESULTS We found significant moderation for amount of alcohol used. Specifically, genetic effects were greater in low-SES conditions, shared environmental effects (i.e., environmental effects that enhance the similarity of twins from the same families) tended to increase in high-SES conditions, and nonshared environmental effects (i.e., environmental effects that distinguish twins) tended to decrease with SES. This pattern of results was found for both income and education, and it largely replicated at a second wave of assessment spaced 9 years after the first. There was virtually no evidence of moderation for either frequency of alcohol use or alcohol problems. CONCLUSIONS Our findings indicate that genetic and environmental influences on drinking amount vary as a function of the broader SES context, whereas the etiologies of other drinking phenomena are less affected by this context. Efforts to find the causes underlying the amount of alcohol used are likely to be more successful if such contextual information is taken into account.