This new finding gives greater credence to theories that predisposition to alcoholism may be inherited as part of a general state of brain overexcitability, writers lead researcher Danielle M. Dick, PhD, a professor of psychiatry at Washington University School of Medicine in St. Louis.
Her report appears in the current issue of the journal Alcoholism: Clinical and Experimental Research.
Alcohol may normalize these overactive brain circuits, which would put a drinker at greater risk of alcohol abuse and dependence, she adds.
In fact, previous studies have identified a major brain chemical known as gamma-amino butyric acid (GABA) that is involved in many nerve pathways affecting alcohol abuse and dependence, writes Dick.
Many effects from alcohol involve GABA -- the difficulty walking, the lessened anxiety, the sleepiness, and even alcohol preference. GABA is also involved in alcohol withdrawal and in the craving for greater amounts of alcohol to soothe nervousness, she explains.
There are several versions of GABA genes. However, the role of these genes in alcohol abuse has been somewhat unclear, she writes.
Her newest study is the first to identify the specific gene variation linked with alcoholism.
Dick's study involved 262 families -- a total of 2,282 adults. Each family was relatively large -- three siblings plus both parents living -- and each family had members who were alcoholics, whether in the immediate family, second-degree relatives (uncles, aunts, nephews, nieces, grandparents), or third-degree relatives (cousins).
All were genetically tested for specific GABA genes. The findings were compared with a similar-sized comparison group.
They found consistent evidence of alcohol dependence and one particular gene that regulates GABA activity -- called GABRG3, writes Dick. No consistent links were found with other variations of the GABA gene, she adds.
"These analyses suggest that GABRG3 may be involved in the risk for alcohol dependence," Dick writes. "These findings support the theory that the predisposition to alcoholism may be inherited as a general state of central nervous system hyperexcitability caused by an altered response to GABA."
Those who develop alcoholism and alcohol abuse may have greater numbers of the GABRG3 genes than their unaffected family members, she adds.
Also, genetic makeup does not necessarily mean that a person is doomed to become an alcoholic, Dick explains in a news release.
"One reason it is so difficult to find genes involved in psychiatric disorders is that there is an interplay between genetic and environmental factors," she says. "A person can carry all kinds of genes that predispose them to alcohol dependence, but if they never take a drink, they won't become an alcoholic."