What Causes Alcoholism?
People have been drinking alcohol for about 15,000 years. Drinking steadily and consistently over time can produce dependence and cause withdrawal symptoms during periods of abstinence; this physical dependence, however, is not the sole cause of alcoholism. To develop alcoholism, other factors usually come into play, including biology, genetics, culture, and psychology.Genetic factors play a significant role in alcoholism and may account for about half of the total risk for alcoholism. The disorder is so complex, however, that no single gene is likely to be a major culprit.
Researchers are investigating a number of inherited traits that make particular individuals susceptible to this disorder. Some examples are the following:
- The amygdala is an area of the brain thought to play a role in the emotional aspects of craving, which can lead to addiction. One study found that the amygdala is smaller in subjects with family histories of alcoholism, suggesting that inherited differences in brain structure may affect risk. Other studies suggest that certain brain chemicals (neurotransmitters) and proteins in the amygdala region may be involved in the link between anxiety and alcoholism.
- Because alcohol is not found easily in nature, genetic mechanisms to protect against excessive consumption may not have evolved in humans as they frequently have for protection against natural threats. Some evidence, then, indicates that a lack of genetic protection plays a major role in alcoholism. Such studies have found that people with a family history of alcoholism tend to "hold their liquor" better than those without such a history. Experts suggest some people may inherit a lack of those warning signals that ordinarily make people stop drinking. Research suggests this factor may contribute to between 40 - 60% of alcoholism cases related to genetic factors. (Even in the absence of genetic factors, repeated exposure to alcohol increases the ability to tolerate larger amounts before experiencing behavioral impairment.)
- Genes that regulate certain chemical byproducts of alcohol are under intense scrutiny. Alcohol is metabolized in a two-stage process: It is first converted to acetaldehyde (AcH), which is then converted into acetate. AcH is being researched because it plays a role in most actions of alcohol, including damaging effects on the liver and upper airway. It also may be protective. For example, some people, particularly in some Asian and Jewish populations, may be less likely to become alcoholic because of a genetic deficiency in AcH, which produces a buildup of acetate after drinking alcohol. Acetate is toxic and in high amounts causes flushing, dizziness, and nausea. Individuals with this genetic factor, then, are less likely to become alcoholic. (This deficiency is not completely protective against drinking, however, particularly if there is social pressure and high exposure to alcohol, such as among college fraternity members.)
- Some people with alcoholism may have an inherited dysfunction in the transmission of serotonin. This is an important brain chemical messenger known as a neurotransmitter. It is important for well-being and associated behaviors (e.g., eating, relaxation, sleep). Abnormal serotonin levels are associated with high levels of tolerance for alcohol. They are also linked to impulsive and aggressive behaviors, which can predispose people to drink and can increase the risk for dangerous behaviors and suicide in alcoholics. (Serotonin abnormalities can also develop from environmental pressures as well, such as early loss in childhood.)
