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Alcoholism: nurture may often outdo nature.

Many scientists involved in the widely publicized search for genes that predispose people to alcoholism frankly acknowledge the tremendous power exerted by environmental influences on uncontrolled imbibing (SN: 9/21/91, p.190). A new study of 356 pairs of identical and fraternal twins supports their position, finding a minimal role for genetic factors in alcoholism among women of all ages and among men whose drinking problems surface during adulthood.

Family influences -- such as expectations about alcohol's mood-altering effects based on a parent's alcoholic behavior -- may importantly predispose members of these groups to alcoholism, report psychologist Matt McGue of the University of Minnesota in Minneapolis and his colleagues. However, genes apparently assume a predominant role among men whose alcoholism emerges during adolescence, usually along with illicit drug abuse and delinquent behavior, McGue's team asserts.

"Researchers may be ignoring the significant influence that the environment has in the origins of alcoholism," the group concludes in the February JOURNAL OF ABNORMAL PSYCHOLOGY. The data weaken claims that alcoholism usually represents a "biologically determined medical disease,' McGue argues.

The researchers studied 85 pairs of male identical twins (sharing the same genes), 96 pairs of male fraternal twins (sharing half of their genes), 44 pairs of female identical twins, 43 pairs of female fraternal twins and 88 pairs of opposite-sex fratneral twins. The team chose one twin who had undergone treatment for alcohol dependence or abuse, then sought out the sibling. Alcohol dependence involves persistent, uncontrolled consumption, a need for increasing amounts of alcohol, and marked withdrawal symptoms. Alcohol abuse, although slightly milder, causes recurrent social, job or physical problems.

Alcohol abuse and dependence, as well as illicit drug abuse and behavior problems, occurred much more often among both male identical twins than among both male fraternal twins, but only when the treated twin had suffered "early-onset" symptoms. Female identical and fraternal twins showed no such discrepancy in their rates of alcohol problems. For opposite-sex twins, alcohol problems appeared most often among the brothers of treated women.

Females in the twin study reported more prior treatment for depression and greater illegal use of prescription drugs than males. This suggests that depression plays a greater role in female alcoholism, the researchers contend.

Although the data emphasize environmental influences on alcoholism, they also indicate that consistent delinquent and cruel behavior derives from important genetic effects, McGue says.

McGue currently directs a prospective study of nearly 650 pairs of twin children, half of whom have an alcoholic parent, aimed at teasing out genetic and environmental influences on the development of alcoholism. He suspects that early-onset males possess an inherited inability to inhibit a spectrum of behaviors involving substance abuse and aggression.

McGue's findings replicate a twin study conducted in the 1970s, notes psychologist Henri Begleiter of the State University of New York Downstate Medical Center in Brooklyn. Begleiter, director of a nationwide study on the genetics of alcoholism, believes environment accounts for most of the disorder. But scientists lack valid ways to measure family environment, he says (SN: 12/7/91, p.376).

An inherited lack of behavioral inhibition may afflict women as well as men, adds psychiatrist Ernest P. Noble of the University of California, Los Angeles. In McGue's study, women exhibited this tendency through depression and prescription drug use, Noble says, but future female samples may show more alcoholism and behavior problems as cultural conventions regarding women change.
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Title Annotation:power of environmental influences
Author:Bower, B.
Publication:Science News
Date:Feb 1, 1992
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