The study, published in the January issue of the journal Alcoholism: Clinical and Experimental Research, is the first to demonstrate an association between this particular gene and alcohol dependence.
The gene is related to a receptor that allows for the movement of Gamma-amino butyric acid (GABA) between nerve cells. GABA is the major inhibitory chemical in the central nervous system.
"There were lines of evidence from other studies -- animal studies, in vitro studies -- that suggested GABA receptors are involved in the behavioral effects of alcohol," says lead author Danielle M. Dick, Ph.D., research assistant professor of psychiatry at Washington University School of Medicine in St. Louis. "Because GABA receptor genes were likely candidates and previous studies had linked this area on chromosome 15 to alcoholism, we zeroed in on three GABA receptor genes but only found significant association with one of them."
The study was conducted as part of the national Collaborative Study on the Genetics of Alcoholism (COGA), an ongoing project involving interviews and DNA samples from more than 10,000 individuals from inpatient and outpatient alcohol treatment centers and their families. Families in the COGA study usually have several members with alcohol dependence.
For this study, the investigators analyzed DNA from 262 families, a total of 2,282 individuals. They isolated three genes on chromosome 15 -- GABRA5, GABRB3 and GABRG3 -- that sit very close together on the chromosome. Then the investigators used markers called SNPs (single nucleotide polymorphisms) to study differences between the participants' genes.