Genetic factors play a major role in the development of alcoholism in women, contrary to the findings of many previous studies, a Virginia researcher said Tuesday. The new findings also indicate that alcoholism is becoming more common in women, probably as a result of relaxation of cultural inhibitions.
In a study of 1,030 sets of female twins, the researchers found that genetics control 50% to 60% of women's susceptibility to alcoholism, with cultural and environmental factors accounting for the rest.
The researchers say their results, reported Tuesday at a medical conference in Marina del Rey and today in the Journal of the American Medical Assn., are more reliable than those of previous studies because they are based on much larger numbers of women. Furthermore, they are nearly identical to similar findings recently reported in men and suggest that genetics play an equal role in both sexes.
Women also seem to be approaching men in the extent of their drinking problems. Previous estimates have suggested that only about 3% of American women, and about 14% of the entire population, develop severe drinking problems.
But the researchers found that 9% of the women in their study, all below the age of 30, suffered from alcoholism and another 8.3% from problem drinking.
"Women in this new generation are beginning to drink just like their fathers did and they are going to suffer all the problems associated with alcoholism that their fathers did," said Dr. Robert Cloninger, a psychiatric geneticist at Washington University in St. Louis.
"This is an excellent study and a very important result," said behavioral geneticist Matt McGue of the University of Minnesota, who reported in 1981 that he found no genetic contribution to women's susceptibility to alcoholism. "This is certainly going to revise the way I think about things."
"The take-home message from this study," said its primary author, Dr. Kenneth S. Kendler, a psychiatrist at Virginia Commonwealth University in Richmond, "is that the biomedical community needs to rethink its position on alcoholism in women." A much greater proportion of women should be included in alcoholism studies that have previously focused primarily on men, he said.
Physicians should also place greater emphasis on family histories of alcoholism when making a diagnosis, he added.
Studies of twins are widely used in medicine to determine whether a specific disorder has a genetic link. If genetics plays a role in the disorder, then the disorder should occur much more frequently among both members of a pair of identical twins (who have identical genes) than among both members of fraternal twins (who share only some genes).
That is what has been observed in studies of alcoholism among male twins and what has now been found in studies of female twins.
Kendler and his colleagues at Washington University and the University of Michigan studied 1,030 pairs of female twins from the Virginia Twin Registry. Each twin was interviewed personally by social workers who used specific criteria established by the American Psychiatric Assn. for determining alcohol-related problems. The worker who interviewed the second twin in each pair did not know the results from the interview of the first twin.
In general, they found that if one member of a set of identical twin had a problem with alcohol, her twin was four to five times more likely to suffer the same problem than were women in the general population. In contrast, if one member of a set of fraternal twins has an alcohol problem, the second twin was only 1 1/2 to two times as likely as other women to suffer the problem.
Using well-established statistical techniques, Kendler and his colleagues were able to calculate that genetics made a 50% to 60% contribution to the alcohol problems. "This means that genes are not trivial (in determining susceptibility to alcoholism), but they are not of overwhelming importance either," Kendler said. "They don't dictate completely whether you will or will not become an alcoholic."
Kendler noted that his study group was much larger than those in previous twin studies, "and thus more likely to be accurate."
Equally surprising, perhaps, was the study's finding that 17% of the young women had a drinking problem, much higher than in previous reports but in line with other studies now under way. The previous paradigm in alcoholism studies was that men are five times as likely as women to be alcoholics, Kendler said, "but now the ratio is closer to 2 1/2 or 2 . . . and men are not drinking less."