A TWIN-FAMILY STUDY OF ALCOHOLISM IN WOMEN

Objective: The authors seek to understand in general the sources of fa milial resemblance for alcoholism and in particular how parents transm it the vulnerability to alcoholism to their daughters. Method: The aut hors interviewed 1,030 pairs of female same-sex twins of known zygosit y from the population-based Virginia Twin Registry and 1,468 of their parents. They examined a narrow definition of alcoholism, requiring to lerance or dependence, and a threshold approach that classified indivi duals either as unaffected or as suffering from one of three levels of severity of alcohol-related problems. Twin-family structural equation models were fitted to the observed tetrachoric or polychoric correlat ion matrices by using asymptotic weighted least squares. Results: In t he best-fitting model from both diagnostic approaches, 1) the familial resemblance for alcoholism was due to genetic factors, with the herit ability of liability estimated at 51% to 59%; 2) genetic vulnerability to alcoholism was equally transmitted to daughters from their fathers and from their mothers; and 3) alcoholism in parents was not environm entally transmitted to their children. Assortative mating for alcoholi sm was found only for the broader definitions of illness. Genetic fact ors that influenced the liability to alcoholism were the same in the p arental and twin generation for the narrow definition of alcoholism. W hen broader definitions were used, these factors, while substantially correlated, were not identical. Conclusions: The transmission of the v ulnerability to alcoholism from parents to their daughters is due larg ely or entirely to genetic factors.