Genes Influence Your Response to Others' Drinking Habits

Your genes may determine how likely you are to imitate the drinking habits of others, new research suggests.

In recent years, scientists have begun to illuminate the reasons some people adapt their drinking behavior to that of other people while others don't. Now, a study shows that the gene for the dopamine D4 receptor (DRD4) may influence one's sensitivity to others' alcohol consumption. The gene has previously been associated with novelty-seeking behavior and dependence on feel-good rewards brought on by, say, chocolate or cocaine.

In a study conducted at the Behavioral Science Institute in The Netherlands, researchers found that participants with a certain version of the DRD4 gene were more likely than others to drink more in response to seeing someone else drink heavily.

The science of bar behavior

In the name of science, the researchers constructed a make-shift bar in a university laboratory. They had participants work in pairs to watch and rate television commercials, and then told them they would have a break, during which they and their partners could wait at the bar.

But each participant was unknowingly paired with a person working with the researchers. These undercover agents were given specific instructions about how many alcoholic drinks to consume while waiting at the bar. The researchers observed the study participants to see if they followed suit.

Genetic analyses revealed that the students who most closely imitated their partner's drinking behavior possessed a version of the DRD4 gene called the 7-repeat allele, while the others didn't.

"Although we tested this among students and not alcoholics," said Helle Larsen, a co-author of the study that is published in the July issue of Psychological Science, "it could indeed mean that it is harder for recovering alcoholics that are carriers of the 7-repeat allele to refrain from drinking when exposed to alcohol cues."

Previous studies have implicated this version of DRD4 in a range of "cue-induced" addictive behaviors, including alcohol, nicotine and heroin use, and overeating. In 2007, scientists at the Central Institute of Mental Health in Germany surveyed 300 adolescents to gather data about alcohol intake and personality traits. Following the survey, the teens' DNA was genotyped. Those who had the 7-repeat allele typically reported drinking more per occasion.

In a 2008 study published in Pharmacogenomics, researchers at Brown Medical School in Rhode Island found that having a copy of this allele increases the difficulty of quitting smoking and increases the likelihood of relapse.

Men and women are equally likely to possess the 7-repeat allele, Larsen said.

An evolutionary explanation

The 7-repeat allele may have a bad rap now, but researchers suspect that it was selected within the last 40,000 to 50,000 years as a survival mechanism. The gene most likely benefitted our early ancestors who had to take necessary risks to find food, shelter and mates, according a 2008 study by Harvard University researchers published in the journal Evolution and Human Behavior.

Still, understanding how the gene is influenced by a 21st century environment could give scientists a new tool for treating addictive behaviors.

Next, Larsen will investigate the imitation of specific sipping behaviors.

"I'm doubtful that the dopamine system can be activated within seconds," said Larsen, "but it's important to really test this alcohol cue-reactivity paradigm and disentangle the exact mechanism."

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