Not all alcoholics are created equal. People differ in why they drink, how they drink and what effects drinking will have on their health and relationships.
A key biological component of the variability in alcoholism may be in the control of signaling by serotonin, a brain chemical that carries messages between nerve cells and mediates the rewarding effects of alcohol.
Scientists at the University of Virginia have found that a variation in the serotonin transporter gene, which regulates serotonin levels, is associated with drinking intensity. The results, which will appear in the February 2009 issue of Alcoholism: Clinical and Experimental Research, were published online yesterday.
Senevirante et al tested six variations in the serotonin transporter gene for association with drinking intensity in 275 alcoholics seeking treatment – 165 were Caucasian and 110 were Hispanic. Women made up 21.5% of the sample.
In the Caucasian sample only, the researchers found that having one or two copies of a C at rs1042173 led to less intense drinking, defined as number of drinks per drinking day. There was no difference in number of drinks averaged over 90 days. People with the AA genotype drank an average of about 11 drinks per drinking day, while those with the AC or CC genotype drank about eight and a half.
(23andMe customers see their data for rs1042173 using the Browse Raw Data feature)
Previous research has linked a separate variation in the serotonin transporter (5-HTTLPR) with alcohol dependence, but results have been conflicting.
The study’s authors point out that in all cases, the number of drinks people had exceeds the threshold for what is considered heavy drinking (five or more standard drinks per day for men and four or more for women). They also note that their study looked only at alcoholics seeking treatment, who may not be representative of alcoholics in general.
In the future, the researchers say they hope to investigate whether rs1042173 can be used to provide more effective treatment for alcoholism by predicting whether medications that affect the serotonin system will work for an individual.