Genetic Aspects of Alcohol Use and Alcoholism in Women.

Genetic studies are a crucial component of alcohol research. These studies attempt to quantify genetic influences on problem drinking; characterize patterns of inheritance; and, ultimately, identify the gene or genes that confer susceptibility to alcoholism. Results of such research have important implications for the prevention, early detection, and treatment of alcoholism. There is reason to believe that the factors influencing alcohol use in general, and alcoholism in particular,(1) are not the same in women as in men (National Institute on Alcohol Abuse and Alcoholism [NIAAA] 1993). Nevertheless, research on the genetics of alcoholism has traditionally used male subjects or has pooled the data in a manner that obscures gender differences. Genetic factors may influence gender differences in alcohol use and alcoholism in two ways. First, the same genetic influences may exist in both women and men, with the observed gender differences being attributable entirely to environmental factors. Second, different (but possibly overlapping) genetic influences may be responsible for the observed gender differences. This article discusses available evidence for distinguishing between these two alternatives based on four types of studies: family, adoption, and twin studies; molecular genetic studies; biological marker studies; and animal studies. FAMILY, ADOPTION, AND TWIN STUDIES Family Studies Family studies examine rates of alcoholism in relatives of the alcoholic and nonalcoholic study subjects (probands). Such studies have consistently found the risk for alcoholism to be 4 to 7 times greater in relatives of alcoholics compared with relatives of nonalcoholics (Cotton 1979; Merikangas 1990). Overall, male relatives are more likely to be alcoholic than are female relatives. Few studies have compared male alcoholic probands and female alcoholic probands with respect to the occurrence of alcoholism among their relatives. In such studies, gender differences are suggested by different rates of transmission of alcoholism to same-gender versus opposite-gender relatives. For example, if the female relatives of female probands have the same prevalence of alcoholism as do the female relatives of male probands, then no gender differences are indicated. However, if the female relatives of female probands have higher (or lower) rates of the disorder than do female relatives of male probands, then gender differences are suggested. In a recent review of the literature, McGue and Slutske (1993) identified only seven family studies that examined alcoholism in female and male relatives (mostly parents) of both female and male alcoholic probands. In general, female and male relatives had similar rates of alcoholism regardless of whether the probands were male or female. Alcoholism was found in 6 percent of female relatives of male probands and 10 percent of female relatives of female probands. Alcoholism was found in 27 percent of male relatives of male probands and 33 percent of male relatives of female probands. Thus, family studies have not found evidence for a different genetic influence on alcoholism in women compared with men. However, the possibility remains that gender-specific genetic influences do exist but are overshadowed by environmental influences. Adoption Studies Adoption and twin studies provide more definitive evidence of genetic influences than do family studies. In adoption studies, alcoholism rates of adopted-away children of alcoholic parents are compared with alcoholism rates of adopted away children of nonalcoholic parents. Genetic influences are indicated by higher alcoholism rates in the children of alcoholic than nonalcoholic parents. Four adoption studies have examined the role of genetic factors in alcoholism in women. In the first study, Roe (1944) determined alcoholism rates in adopted daughters whose biological fathers were heavy drinkers. …