Which Genetic Factors Increase Susceptibility to Alcoholism?

Doctors and researchers know that some of the risks for developing alcoholism are passed on genetically from generation to generation. In a study published May/June 2014 in the journal Alcohol and Alcoholism, researchers from the Medical University of South Carolina and the University of California, Los Angeles assessed the potential impact of two genetic variations that can make any given person more likely to perceive alcohol consumption as a rewarding or pleasurable experience. These researchers concluded that the two variations apparently produce their alcoholism-related risks when they appear in an individual together rather than separately.

The Basics

The National Institute on Alcohol Abuse and Alcoholism estimates that, for any individual, roughly 50 percent of the chance of developing alcoholism comes from genetic factors. However, these factors are not very simple or straightforward. Instead, they stem from the complex interaction between a number of genes within the individual. It’s important to note here that not all genes behave in the same way in all people; instead, many genes exist in two or more versions. Depending on the version of a gene you have, that gene can have widely varying effects on your health and wellbeing. To complicate things even further, a specific version of one gene may only have a positive or negative impact on your health when it appears along with a specific version of another gene, or specific versions of a number of other genes. While some people have genetic variations that make them more susceptible to alcoholism, others have genetic variations that actually make alcoholism substantially less likely to occur.

Two Key Genes

Research has shown that two genes, in particular, appear to have a strong influence on a person’s chances of developing alcoholism. One of these genes affects how sensitive the brain is to alcohol-related pleasure. When a person repeatedly consumes substantial amounts of alcohol, it creates a long-lasting change in the brain’s pleasure center that largely accounts for the onset of physical dependence and addiction. The other gene prominently associated with alcoholism risks helps determine how rapidly alcohol enters the brain and produces its classic pleasurable effects. As is true with many other important genes in the body, there are multiple possible versions of these two key alcoholism-related genes. One version of the pleasure-related gene makes the brain more sensitive to the pleasurable impact of alcohol intake. One version of the alcohol uptake gene makes the brain more likely to feel rapid effects from alcohol exposure.

Combined Impact

In the study published in Alcohol and Alcoholism, the UCLA and Medical University of South Carolina researchers sought to determine what happens when the genetic variation that makes the brain more sensitive to alcohol-related pleasure appears at the same time as the genetic variation that allows alcohol to access the brain relatively rapidly. Specifically, they wanted to know if people simultaneously affected by these genetic variations have a stronger self-perceived response to drinking. Such a response is known for its potential to lead to increased alcohol consumption and boost a person’s chances of eventually qualifying for an alcoholism diagnosis. After performing an initial genetic analysis, the researchers gave either IV (intravenous) infusions of alcohol or IV infusions of saline solution to a group of 43 adults affected by alcoholism. Next, they asked all of the participants to report their self-perceptions of the effects that the infusions produced in them. After performing an additional analysis, the researchers concluded that the responses to alcohol exposure were highest in those individuals who had both the genetic variation that increases alcohol-related pleasure levels and the genetic variation that gives alcohol easier access to the brain. They also concluded that the intensity of the responses in these individuals rose along with blood alcohol content as measured by a Breathalyzer test.

Significance and Considerations

Overall, the researchers concluded that the impact of the genetic variation that gives alcohol ready access to the brain largely depends on the presence of the genetic variation for increased sensitivity to alcoholism-related pleasure. This conclusion supports the findings of previous researchers who have investigated the brain reactions that make any given individual more susceptible to the effects of drinking.  

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