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Researchers have identified a genetic factor that may predispose young people to harmful drinking habits. A team of scientists interviewed college students about their alcohol consumption and then analyzed their genetic profiles, or genotypes. They found that students who shared a particular variant of the serotonin transporter gene (5HTT) consumed more alcohol per occasion, more often drank expressly to become inebriated, and were more likely to engage in binge drinking than students without the variant. The study appears in the September 2003 issue of the journal Alcohol and Alcoholism (Volume 38, Number 5)..

"This research provides important new evidence that the risk of developing a maladaptive pattern of alcohol consumption is influenced by genetically determined neurobiological differences that exert their effects during young adulthood," says Ting-Kai Li, M.D., director of the National Institute on Alcohol Abuse and Alcoholism (NIAAA).

NIAAA clinical investigators Paolo B. DePetrillo, M.D., and Research Fellow Aryeh I. Herman B.A., along with researchers from George Washington University in Washington, D.C., conducted the study of 262 male and female college students and analyzed data from the largest homogenous group: 204 male and female Caucasian college students aged 17 to 23 years. To assess the frequency and patterns of alcohol consumption, the scientists asked all the students a set of questions, for example, how many times in the past two weeks they had engaged in binge drinking (five or more drinks for men and four or more drinks for women on one occasion).

The research team also analyzed each student's genotype with a focus on the 5-HTT gene, which is involved in recycling the chemical serotonin after it is secreted into the synapse of a cell. The researchers determined which students had long or short versions of this so-called serotonin transporter gene.

Everyone inherits two copies of each gene, one from each parent. There are two normal variations, or polymorphisms, of the serotonin transporter gene, labeled the long and the short variants. Most people are heterozygous, that is, they have one copy of each variant, but about 30 percent of the Caucasian population are homozygous (carry duplicate copies) of either the long or the short version. This percentage varies depending on the ethnic background of the individual.

The researchers found that the students who carried two copies of the short version of 5-HTT were more likely to report troublesome drinking patterns. Dr. DePetrillo says, "Our findings reveal a significant association of the serotonin transporter promoter polymorphism with increased alcohol consumption behavior in the students that we studied. Taken together with other research, this finding suggests that genetically mediated differences in serotonergic response play an important role in mediating patterns of alcohol intake." The students with two copies of the short form of the gene engaged more frequently in binge drinking, drank more often to get drunk, and consumed more alcoholic drinks per occasion than did students with the other genotypes.

Another difference the researchers observed was that students with at least one copy of the long variant of the 5-HTT gene tended to consume a smaller number of drinks at a sitting, even though they went out to drink as often as the other students.

Why should the presence of the shorter gene variant make such a difference? The authors speculate that, because individuals who are homozygous for the short version are known to be at risk for higher levels of anxiety, they may use alcohol to reduce tension. Further studies are needed to understand the influence of the serotonin transporter gene on drinking behavior, with special attention given to replication in other ethnic groups.

Source: National Institute on Alcohol Abuse and Alcoholism