A new study from researchers at the University of Virginia Health System suggests that a serotonin transporter gene -- SLC6A4 -- significantly influences the level of drinking intensity among heavy drinkers.

The researchers studied the associations between six DNA sequence variations of the serotonin transporter gene with the degree of alcohol consumption among 275 individuals seeking alcohol-related treatment. "Of the six variants examined in the study, we found that one variant … showed a significant association with drinking intensity," said study co-author Ming Li.

Serotonin mediates the rewarding effect of alcohol. Previous research has identified the relationship between the brain's serotonin system and alcohol preference and consumption, and the role that serotonin plays as a factor leading to alcohol abuse.

"But chronic drinking reduces serotonergic function, leading to a serotonin-deficient state," said study co-author Bankole Johnson. "One hypothesis is that alcoholics drink to alleviate this serotonin-deficient state."

Johnson said that being able to identify a genetic marker to sub-type alcoholics may help practitioners "better determine treatment methods that can target specific underlying molecular mechanisms."

The study appeared in the February 2009 issue of the journal Alcoholism: Clinical and Experimental Research.