Sex differences in the sources of genetic liability to alcohol abuse and dependence in a population-based sample of US twins

Background: There are substantial sex differences In all levels of alcohol involvement among U.S, adults. The god of this study eras to test whether t he magnitude and sources of genetic and environmental influences on liabili ty for alcohol abuse and dependence differ for men and women. Methods: Structured personal interviews were used to assess DSM-III-R- and DSM-IV-defined alcohol abase and dependence among 5091 male and 4168 female twins (including 1546 identical, 1128 same-sex fraternal, and 1423 opposit e-sex pairs) born in Virginia between 1934 and 1974. Twin correlations were analyzed using structural equation modeling. Results: The magnitude of twin-pair resemblance was similar across several definitions of alcoholism and was substantially higher among identical than fraternal pairs. The proportion of population variation in liability attri buted to genetic factors was substantial among bath women (55-66%) and men (51-56%), and we found little evidence of a role of environmental factors s hared by family members. In all definitions studied, we could reject a mode l that the genetic sources of liability in the two sexes overlap completely . Conclusion: In this first population-based study of alcoholism among male a nd female twins from the US., we found that genetic factors play a major ro le in the development of alcoholism in both sexes, that the magnitudes of g enetic influence were equally high for men and women, and that the genetic sources of vulnerability are partially, but not completely, overlapping in men and women.