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WEDNESDAY, Aug. 18 (HealthDayNews) -- Some people can drink a lot of alcohol without becoming addicted, and specific genes may help explain why, researchers say.

In a new study of Australian twins, scientists found that separate genes appear to be responsible, to some degree, for dependence on alcohol -- addiction -- and how much people drink. Understanding how these genetic factors work together should give researchers more insight into treatment of alcoholism in its various forms, said study co-author John B. Whitfield, a researcher at Royal Prince Alfred Hospital in Australia.

Alcoholism and alcohol consumption may appear to be similar, but researchers are increasingly studying them separately. Consumption refers to the amount of alcohol that someone drinks, while addiction refers to a person's inability to go without a drink.

"The transition from social alcohol consumption to alcohol dependence is a gradual process, and it is often hard to notice it," said Dr. Alexei B. Kampov-Polevoi, an assistant professor of psychiatry at Mount Sinai School of Medicine. "As a result, many alcoholics and their family members continue to think that a person 'just drinks too much' while this person already developed alcohol dependence and requires treatment."

Whitfield and his colleagues examined statistics about alcohol use from three studies of Australian twins completed between 1980 and 1995. The number of twins in the studies declined from 8,184 in 1980 to 3,378 in 1995.

The findings appear in the August issue of Alcoholism: Clinical & Experimental Research.

The researchers found twins who were genetically similar were more likely to consume similar amounts of alcohol. According to the study, some genes affected both addiction and alcohol intake, while some just affected addiction.

"We found (as others have also found) that alcohol dependence is partly, but not entirely, due to genetic differences between people who are affected by it and those who are not," Whitfield said. "We also found that variation in the amount of alcohol that people habitually drink is subject to genetic influence, and that there is some -- but not complete -- overlap between the genes affecting these two things."

Howard J. Edenberg, professor of biochemistry and molecular biology at Indiana University, said the findings -- that genes separately affect alcoholism and drinking -- are "reasonable." But "that is a long way from identifying individual genes that actually are involved," said Edenberg, whose own research is looking into that area.

So what should ordinary folks take from this study? "There is no direct and new message for people with alcoholism in their families; they are at higher risk than average but this has been known for some time and there is only a statistical risk, not a certainty by any means," Whitfield said. "The more positive message for such people, and the community at large, is that we are learning more about alcohol use and alcohol-related problems and their causes."

More information

The National Library of Medicine more about alcohol abuse and alcoholism.

(SOURCES: John B. Whitfield, Ph.D., researcher, Royal Prince Alfred Hospital, Sydney, Australia; Alexei B. Kampov-Polevoi, M.D. Ph.D., assistant professor, psychiatry, Mount Sinai School of Medicine, New York City; Howard J. Edenberg, Ph.D., professor, biochemistry and molecular biology and of medical and molecular genetics, Indiana University School of Medicine, Indianapolis; August 2004 Alcoholism: Clinical & Experimental Research)

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