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Alcoholism (known formally as alcohol dependence) is one of the two overlapping conditions that form the basis for making a diagnosis of alcohol use disorder. Doctors and researchers know that some of the risks for developing alcoholism are genetically based, while others come from non-genetic influences. In a study published in February 2014 in the journal Alcoholism: Clinical & Experimental Research, researchers from eight U.S. institutions identified three distinct genetic risk groups for inheriting alcoholism. The chances of developing diagnosable alcohol dependence varied among these three groups from low to high.
Alcoholism stems from changes in everyday brain chemistry that cause the brain to treat the presence of at least some alcohol (ethyl alcohol) as a prerequisite for its normal function. Typically, these changes appear in people who consume heavy or excessive amounts of alcohol consistently over extended periods of time, although the amount and length of alcohol exposure necessary to produce the required brain alterations vary somewhat from person to person. Prior to May 2013, alcoholism (alcohol dependence) was considered a distinct condition under the widely accepted mental health criteria developed by the American Psychiatric Association (APA). However, in response to a growing scientific consensus on the overlap between chemically dependent alcoholism and non-chemically dependent alcohol abuse, the APA created alcohol use disorder, an overarching mental health condition that includes mild to severe forms of both alcoholism and alcohol abuse.
In any given individual, the rate and length of alcohol consumption (and other non-genetic factors) combine with genetic risk factors to determine the overall chances of developing alcoholism. All told, genetic factors account for roughly 50 percent of this overall risk, the National Institute on Alcohol Abuse and Alcoholism reports. Despite some popular conceptions, the human body does not contain a single gene that produces alcoholism in its “on” position or prevents alcoholism in its “off” position. Instead, a multitude of genes create both direct and indirect alcoholism-related risks.
Known effects of various alcoholism-related genes include making the body more or less sensitive to alcohol’s intoxicating impact, increasing or decreasing a given person’s likelihood of seeking out highly stimulating experiences and making the body more or less sensitive to hangovers and other alcohol-related side effects. All told, a family history of alcoholism predicts alcoholism more often than any other single variable. However, since genetic mixtures change both within generations and from generation to generation, an individual may have substantially different alcohol-related genetics than his or her parents or other relatives.
In the study published in Alcoholism: Clinical & Experimental Research, the multi-institution U.S. research team used an examination of 2,322 individuals to explore the genetic risk factors for alcoholism. These individuals, all of whom shared European ancestry, came from 118 hereditary bloodlines that are known to be highly affected by alcohol dependence problems. At the time the bulk of the study was conducted, alcoholism still held separate status as a diagnosable condition. The researchers looked for a total of seven diagnosable symptoms of this condition in each participant.
The researchers concluded that about 61 percent of the alcoholism-related symptoms in their participant group came from genetically inherited risk factors. Roughly half of all the participants (identified as “low-risk” in genetic terms) had few or no symptoms of alcoholism, and subsequently did not qualify for a diagnosis of the disorder. Another 33 percent of the participants (identified as “moderate-risk” in genetic terms) had a significant number of alcoholism symptoms; almost half of the members of this group (48 percent) had enough symptoms to qualify for an official diagnosis. In addition, 17 percent of the participants (identified as “high-risk” in genetic terms) were heavily affected by alcoholism symptoms; fully 99 percent of the members of this group had enough symptoms to qualify for an official diagnosis.
The authors of the study published in Alcoholism: Clinical & Experimental Research concluded that one specific genetic alteration appeared consistently in the members of the “high-risk” group. This alteration affects the normal processing of the mineral sodium. Another genetic alteration affecting the normal sense of smell also appeared with some regularity in both the “moderate-risk” and “high-risk” groups. There are two important caveats to the results of this study. First, since it involved only people of European ancestry, it tells only part of the story of inherited alcoholism risks in the overall U.S. population. In addition, the combined symptom list for alcoholism and alcohol abuse underwent minor but significant change when the American Psychiatric Association created alcohol use disorder. This means that some people in the study diagnosed with alcoholism may not qualify for an alcohol use disorder diagnosis under current guidelines.