Alcoholism Health Article

Earlier genetic studies

MULTIGENERATIONAL STUDIES The first studies of the genetics of alcoholism were performed in the 1960s. One investigator noted that the brain wave patterns in alcoholics are lower in height (amplitude) than those of normal people and studied children of alcoholics to determine whether this brain wave pattern might be hereditary. He used two groups of boys between the ages of six and 18, one group comprised of sons of alcoholic men. More than 35% of the sons of alcoholics had the brain wave pattern characteristic of alcoholism, whereas fewer than 1% of the boys in the control group had it. Another multigenerational brain wave study involved type 2 alcoholism, a variant of the disorder in which the alcoholic's father is always an alcoholic. This study found that 89% of the sons of type 2 alcoholics had the characteristic brain wave pattern.

Other studies of children of alcoholics have focused on the effects of alcohol on the body. A study published in 1991 reported that the sons of alcoholics perform better on tests of hand-to-eye coordination after drinking a specified amount of alcohol than the sons of nonalcoholics who had consumed the same amount. The researchers hypothesized that low sensitivity to the effects of alcohol may point to higher levels of alcohol consumption in adult life.

TWIN STUDIES Studies of twins performed in Finland and the United States indicate that people with an alcoholic monozygotic (identical) twin have a significantly higher risk of becoming alcoholics than people with alcoholic dizygotic (fraternal) twins.

STUDIES OF ADOPTED CHILDREN A longitudinal Swedish study known as the Stockholm Adoption Study was performed on children of type 2 alcoholics reared by adoptive parents. The researchers reported in the mid-1980s that 34% of these children became alcoholics in adult life, even when they had been reared by adoptive parents who abstained from alcohol.

Another longitudinal study of adopted children done at the University of Kansas Medical School found that sons of alcoholic parents were four times as likely to become alcoholics as sons of nonalcoholics, even if they had been separated from their parents shortly after birth and reared by nonrelatives with no history of problem drinking. On the other hand, the sons of nonalcoholic parents had a low rate of alcoholism in later life even if their adoptive parents were alcoholics. Studies of adopted daughters yielded less clear-cut results.

STUDIES OF GENDER AND ETHNIC VARIABLES It has been known for several decades that different nations and ethnic groups have widely varying rates of alcoholism, with Ireland, the countries of the former Soviet Union, and the Baltic countries having relatively high rates. Far Eastern and Mediterranean countries (with the exception of France) have relatively low rates. With regard to Asians, researchers have found that a large proportion of the general population—as high as 50% among the Japanese and Koreans—has an aldehyde dehydrogenase deficiency, related to a variation in a gene known as the ALDH2 gene. People with this deficiency experience a disulfiram-like reaction to small amounts of alcohol, which appears to protect them from becoming alcoholics.

Studies of women indicate that Caucasian women in the United States have a higher rate of aldehyde dehydrogenase deficiency than men. It is not known, however, how important this factor is in explaining the overall lower rate of alcoholism among women. One study of Australian twins found that the variation in the ALDH2 gene that decreases the risk of alcoholism in men does not have this protective effect in women. Race and ethnicity affect both patterns of alcohol consumption in women and physical vulnerability to the effects of alcohol. Although African American women and Caucasian women are equally likely to be heavy drinkers, African American women are more likely than Caucasians to abstain from alcohol (46% versus 34%). Among Hispanic women, American-born Hispanics are more likely to be moderate or heavy drinkers than Hispanic immigrants.

Another important variable in assessing the role of ethnicity in alcohol dependence is educational attainment. According to one 2000 study, low levels of educational attainment are correlated with alcohol dependence among African Americans, while high levels of education are associated with alcohol dependence among Caucasians. Another 2000 study found that dropping out of high school was associated with an increased risk of alcohol abuse among both groups, while entering college without completing the course of studies was associated with a higher rate of alcohol abuse only in Caucasians. The long-term effects of educational level on alcohol dependence in different subcultures, however, require further study.

STUDIES OF BRAIN TISSUE In 1990, researchers at UCLA and the University of Texas studied tissue samples from the brains of 70 deceased persons (men and women from a variety of ethnic groups); half the samples were from known alcoholics. Of the tissue samples from alcoholics, 69% had an abnormal gene for dopamine reception whereas 80% of the nonalcoholics' samples had a normal gene. Dopamine is a neurotransmitter associated with a sense of pleasure; its receptor gene is located on human chromosome 11. The researchers speculated that the atypical form of the gene may direct the formation of defective dopamine receptors in the brain, which in turn may cause the person to crave alcohol and other substances that increase the body's dopamine production.