The Genetics of Alcoholism

Recent studies have demonstrated that alcoholism is more than the result of environmental causes and conclude that alcoholism can be inherited. For instance, it was shown that identical twins are much more likely than fraternal twins to resemble each other in terms of having alcoholism. Heath, Bucholz, Madden et al concluded that up to 60% of the risk of alcoholism is determined by genetic factors. This conclusion is applied to both men and women.

Several genes may contribute to alcoholism. It is important to understand that carrying these genes only make a person more susceptible to alcoholism, it doesn't mean that they will suffer from alcohol addiction. For a person to become an alcoholic several environmental factors have to trigger that behavior.

There are several genes that affect how the body metabolizes alcohol. For instance, genetic variants in the enzymes alcohol dehydrogenase (ADH) or aldehyde dehydrogenase (ALDH), found frequently in the Asian populations, affect the conversion of alcohol to a breakdown product known as acetaldehyde. This causes facial flushing, nausea and a rapid heart beat. The adverse reaction stops people with these genetic variants from drinking too much. Consequently, the number of people who suffer from alcohol addiction is smaller in Asian populations compared to other ethnic groups.

Using micro-array, it is now possible to find alcohol-related genes. Several candidate genes associated with alcohol preference have been found to encode neurotransmitter receptors and neurotransmitters. For instance, neuropeptide Y (NPY) has been found to affect the response to alcohol in rats. Other genes have been found that express differently in the brain regions of alcohol–preferring rats than they do in control groups.

Rats bred to prefer alcohol have lower levels of NPY and they experience seizures when alcohol is withdrawn. When NPY is administered, those seizures fall off in number. NPY receptor genes have also been implicated in withdrawal symptoms in humans.

Genetics research allows us to understand at the individual level how we respond to alcohol. It also helps to understand what might cause a person to become susceptible to alcohol addition. We can use genetic research to identify people at high risk of alcoholism and apply preventive measures to reduce the risks of such an event. Furthermore, we can also use these results to quantify the effects of environmental factors on alcoholism.

Heath, A.C.; Bucholz, K.K.; Madden, P.A.F.; et al. Genetic and environmental contributions to alcohol dependence risk in a national twin sample: Consistency of findings in women and men. Psychological Medicine 27:1381–1396, 1997.

Heath, A.C., and Martin, N.G. Genetic influences on alcohol consumption patterns and problem drinking: Results from the Australian NH&MRC twin panel follow–up survey. Annals of the New York Academy of Sciences 708:72–85, 1994.

Howard J. Edenberg & Tatiana Foroud, The genetics of alcoholism: identifying specific genes through family studies, Addition Biology, 2008