On average, women born before 1944 began drinking at age 20. Those born after that started drinking alcohol at age 17, and they had a 50 to 80 percent greater risk for alcohol dependence, the researchers found.

"We had previously noted that women were catching up with men in their rates of drinking and alcohol dependence, and this earlier age at which they began drinking helps explain that finding," says Richard A. Grucza, Ph.D., assistant professor of psychiatry and first author on the study. "An early age at the onset of drinking is a strong predictor of subsequent alcohol dependence. About one in three individuals who start drinking at age 17 or younger become alcohol dependent. For those who wait until age 21 or older, that number is one in ten."

In April, Grucza's team reported that women are catching up with men in alcohol use and dependence. They found substantial increases in drinking and alcohol dependence among women born between 1944 and 1983, compared to those born between 1934 and 1943. The new research, published in the August issue of Alcoholism: Clinical & Experimental Research and currently available at OnlineEarly, focuses on the ages at which men and women began to drink.

The researchers compared data from two surveys of alcohol use: the National Longitudinal Alcohol Epidemiologic Survey, gathered in 1991 and 1992, and from the National Epidemiologic Survey on Alcohol and Related Conditions, which was compiled 10 years later.

"In our previous work, we found that women born after 1944 had a substantially higher risk for alcohol dependence compared to those born prior to that," Grucza says. "Now we have found that women born during this 'high risk' period also began drinking earlier than their predecessors, and this earlier drinking might explain the higher rates of alcoholism. As the age of drinking onset got lower for women, the rates of alcohol dependence increased."

Both men and women born between 1944 and 1963 began drinking at younger ages than those born between 1934 and 1943. But the drop in age at the time that drinking began was twice as large in women (3.2 years) as it was in men (1.6 years).

Grucza says there has been controversy in the field of alcohol research over whether starting to drink at a younger age actually increases risk of alcohol dependence or whether that younger age at first drink is a marker for other risk factors, such as family environment, impulsivity, or other genetic traits and/or environmental factors that can influence risk.

Although some past research has linked a genetic predisposition to alcohol dependence with early-age drinking, Grucza says genetic changes alone can't explain the increases in alcohol dependence among women in this study.

"Since genes don't change over such a short of a period of time, genetics can't be the whole story," he says. "There is a lot of discussion about whether the minimum drinking age should be lowered again. Our findings would suggest that from a public-health point of view, lowering the legal drinking age might lead to increased rates of alcohol dependence."

An interesting sidebar to the current study is that between 1970 and 1975, 29 states lowered the legal drinking age. Those laws were reversed 10 years later, but during the 1970s, when many of the women in these studies took their first drinks, it was legal to consume alcohol at age 18 rather than 21.

Legal drinking age, Grucza says, is one of many factors influencing when a person begins to drink, and in future studies he and his colleagues plan to look more closely at the effects of drinking-age laws on both when a person begins to drink and their subsequent risk for alcohol dependence.

Grucza RA, Norberg K, Bucholz KK, Bierut LJ. Correspondence between secular changes in alcohol dependence and age of drinking onset among women in the United States. Alcoholism: Clinical and Experimental Research, vol 32 (8). August 2008 DOI: 10.1111/j.1530-0277.2008.00719.x

This study was supported by the National Institute on Alcohol Abuse and Alcoholism and the National Institute on Drug Abuse of the National Institutes of Health.

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