One of the characteristics that may be genetically influenced is how much alcohol a person requires to get the desired effect.

The study, which appears in the November issue of Alcoholism: Clinical & Experimental Research, may one day have implications for prevention of this disease.

"Genes don't cause alcoholism, genes contribute to characteristics that contribute to alcoholism," explained Dr. Marc A. Schuckit, first author of the study and director of the Alcohol Research Center at Veterans Affairs San Diego Healthcare System.

"If you can study people with that gene variation who don't develop alcoholism and who do develop alcoholism, you might be able to develop prevention techniques that are more likely to be more effective for that specific gene variation," he said.

Genetically Influenced

Dr. Gopal Upadhya, medical director of the Areba Casriel Institute, a substance-abuse treatment center in New York City, called the new research "a very interesting study but it's not fully conclusive. This may open the door for a lot of other investigations."

Alcohol dependence is genetically influenced, with genes explaining about half the risk, Schuckit said. It's not likely there is one gene for alcoholism, but several that influence characteristics that predispose a person to alcoholism.

A person's social history as well as what they perceive as normal consumption also contribute to the risk, Upadhya added.

One of the characteristics that may be genetically influenced is how much alcohol a person requires to get the effect they desire.

"This need for a lot of booze to have an effect probably contributes to the probability that when you do drink, you're going to drink a lot more, which leads to the development of tolerance and hanging out with other people who drink a lot," Schuckit explained.

Level of Response

Schuckit and his colleagues wanted to try to find the genes linked to this level of response to alcohol.

So, they examined 238 pairs of siblings, 18 to 29 years old, all of whom had had some experience with alcohol but were not dependent. All the participants had at least one alcoholic parent and most were white and relatively highly educated.

All participants were given "oral alcohol challenges," during which they drank ethanol mixed with a carbonated, sugar-free beverage, the equivalent of about three drinks. Level of response was ascertained by asking subjects to rate whether they were feeling dizzy, nauseated, happy or intoxicated.

Blood samples from siblings and at least one parent were then genotyped to see if there was any relationship between level of response and chromosome region.

"It turns out there's an area on chromosome 10 that we have been interested in in the past that is related to level of response in the current study," Schuckit said. "We show that this area is of super interest."

'Everything Is in Prevention'

One gene in particular, called KCNMA1, looked interesting. The gene had already been linked to the intensity of alcohol's effect in worms. "While our study didn't definitely demonstrate that that particular gene is the one we're looking for, it was suggestive that it's worth looking further," Schuckit said.

Now, the researchers are widening their search, looking at more people to see if the same gene variation is important.

"Everything is in prevention," Schuckit said. "The whole purpose of this series of studies is to find genes related to characteristics and to study those genes in relation to alcohol-influencing characteristics, to try to find ways to help people be resilient when they're carrying the particular gene."

A second study in the same journal found that consumers, especially women, may be underestimating how much alcohol they're actually drinking because drink sizes can vary. If people can't keep track of how much they're drinking, it's hard to confirm to safe-drinking guidelines, the authors stated.

More information: To learn more about the causes and treatments of problem drinking, head to the National Institute on Alcohol Abuse and Alcoholism.