In the first major twin study to compare genetic and environmental factors that contribute to the risk of alcoholism in both sexes, researchers have found that genetics plays an important role in determining alcohol dependence in women as well as in men. The study contradicts the long-held assumption that a woman's environment is more likely to influence whether she becomes dependent on alcohol.
The study was conducted by scientists at Washington University School of Medicine in St. Louis and Australian collaborators at the Queensland Institute of Medical Research. It was funded by the U.S. National Institute of Alcoholism and Alcohol Abuse, and the findings were published in a recent issue of the journal Psychological Medicine.
While there is ample evidence for an important genetic influence on alcoholism risk in men, the tie between genetics and alcoholism in women has been uncertain, said the paper's lead author, Andrew Heath, Ph.D., a professor of psychiatry at Washington University.
The study sought to address this shortcoming. It involved 2,685 pairs of twins, all participants in an adult twin study started in Australia in 1978 and maintained by the Australian National Health and Medical Research Council. The two members of each pair were raised in the same home environment. The study included -- for the first time -- twins of opposite sex as well as twins that were either both male or both female.
Telephone interviews with the twins were conducted to assess whether the participants had lost control over their drinking, were unable to cut back on drinking or had similar problems with alcohol.
Twins who had an alcoholic identical twin were much more likely to be alcoholic themselves than were twins who had an alcoholic fraternal twin, and this was equally true in women and in men. More surprisingly, men who had an alcoholic twin sister had very high rates of alcoholism.