Young women who transition from taking their first drink to becoming alcoholics have a stronger influence from genetics. School of Medicine researchers found that although environment is most influential in determining when girls begin to drink, genes play a larger role if they advance to problem drinking and alcohol dependence.
The researchers studied 3,546 female twins ages 18-29 to ferret out the influences of genes and environment in the development of alcohol dependence. Their findings appear in the April issue of Alcoholism: Clinical & Experimental Research.
The road to alcohol dependence involves transitions through many stages of drinking behaviors: from the first drink to the first alcohol-related problems (such as drinking and driving or difficulty at school or work related to alcohol use) to alcohol dependence.
Environmental factors the twins shared, such as exposure to conflict between parents or alcohol use among peers in school, exerted the largest influence on initiation of alcohol use. The study found that females who had their first drink at an earlier age were more likely to develop serious alcohol problems. The researchers found that all transitions were attributable in part to genetic factors, increasing from 30 percent for the timing of first drink to 47 percent for the speed at which women progressed from problem drinking to alcohol dependence. But genetics did not explain everything.
“Even when genetic factors are most influential, they account for less than half of the influence on drinking behavior,” said lead author Carolyn E. Sartor, Ph.D., a postdoctoral research fellow at the School of Medicine. “That’s good news in terms of modifying these behaviors and reducing the risk of developing alcohol dependence. Genetics are not destiny, and our findings suggest that there are opportunities to intervene at all stages of alcohol use.”
Sartor’s team collected alcohol-use histories from telephone interviews to determine when these women made transitions from one drinking milestone to the next. They studied twins to get an idea of the genetic influences on those transitions. Identical twins share 100 percent of their genetic material, and fraternal twins share about half. So when identical twin pairs are found to be more similar on a given behavior than fraternal twin pairs, this suggests that genetics are playing a role in that behavior. The researchers used this twin-based design to estimate the contributions of genes versus environment to the rate at which women progressed through stages of alcohol use.
“Alcohol dependence is a psychiatric disorder, but drinking alcohol in moderation is normative and is a part of many cultural traditions,” Sartor said. “For example, 85 percent of women in our study reported having at least one drink in their lifetimes, whereas only about 7 percent became alcohol dependent.”
Past studies have focused more on men than women, but Sartor said it is important to study both sexes because risk factors that contribute to alcohol problems differ somewhat between males and females. She also said this study helps to dispel the myth that alcohol dependence is a disorder exclusive to middle-aged men. In the United States, the prevalence of alcohol use disorders is highest among those ages 18-29.
“Much of the heavy drinking that occurs in the young-adult years is actually problem drinking,” she said.
“What once was perceived as partying a little too much is now being recognized as a potentially serious problem,” she said.