Genetic Influence On Alcoholism

Scientists have long recognized that certain genes carry increased risks of alcoholism.

However, this stems from a number of complex variables, and relatively little was known about the most dangerous gene interactions. But a 2014 Translational Psychiatry study has now discovered 11 genes that predict alcoholism with reasonable accuracy.

Genetic influence accounts for 50% chance of alcoholism

As of May 2013, doctors in the U.S. do not officially diagnose alcoholism as an independent condition. Instead, they view its symptoms as indications of a more comprehensive condition called “alcohol use disorder,” which also alcohol abuse in people without physical dependence. In any yearlong timeframe, people affected by alcohol use disorder have at least two symptoms and as many as 11 symptoms attributable to alcohol abuse and/or alcoholism.

Genetic influence accounts for approximately 50% of any person’s chances of developing alcoholism, the National Institute on Alcohol Abuse and Alcoholism reports. However, the genetic factors for physical dependence/alcoholism are not simple or straightforward. Instead, within each individual, a number of genes work together or at cross purposes to determine an overall level of inherited susceptibility. To complicate things even further, some genes have a direct impact on increasing or lowering alcoholism-related risks, while others have an indirect impact that depends on the influence of other relevant factors.

In addition, the specific effects of both direct and indirect genetic influences can vary significantly depending on the environmental risks for alcoholism a person encounters during their lifetime. Scientists have developed a special field of inquiry, called “epigenetics,” to explore the overlapping and opposing genetic variables for alcoholism and a range of other health problems.

Which genes act as predictors for alcoholism?

In the Translational Psychiatry study, American and German researchers used data from a large-scale German project to identify as many alcoholism-related genes as possible. All told, they flagged 135 genes that can potentially directly or indirectly increase or lower alcoholism risks. Next, the scientists used laboratory experiments on mice to determine which of these 135 genes make it more likely that a person will choose to drink alcohol in response to stressful situations. At the end of this second phase of the study they identified 11 candidate genes, which can take a total of 66 specific forms in humans.

In the next phase, the researchers used three groups of human test subjects—African-Americans, European-Americans and Germans—to test the relevance of the 11 identified genes as predictors of the odds of developing diagnosable alcoholism. They concluded that, for each of the groups under consideration, screenings done on the 11 candidate genes can accurately predict which people will develop the symptoms of alcoholism and which people will not develop the condition.

The study’s authors note that the predictive power of screenings for the 11 identified genes is highest when those screenings involve large numbers of people. In any single person, environmental influences can substantially alter the predictions.

Still, the researchers consider their work to be a significant advance in the understanding of the genetic basis of alcoholism and the development of tools to combat it. They also note that some of the 11 genes they characterized as alcoholism predictors can also potentially help anticipate other major health concerns, including schizophrenia, diagnosable cocaine problems, anxiety disorder, bipolar disorders and Parkinson’s disease.

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