A study led by researchers at Columbia and Yale University and published in Biological Psychiatry in May 2018 adds to the large and growing body of research that supports the view that substance use disorders are brain diseases with powerful effects on thinking and behavior, and that there are genetic variations that affect the development and progression of these disorders. This is the perspective endorsed by the National Institute on Drug Abuse, the National Institute on Alcohol Abuse and Alcoholism and the American Society of Addiction Medicine.
The results of this study speak to the important matter of heritability in alcohol use disorders. Recent research indicates that 50 to 60 percent of the risk for alcoholism is determined by an individual’s genetic make-up. But what particular risk factors are passed along in families where alcohol use disorders (AUDs) are prevalent? Answering this question could lead to more effective strategies for both pharmacological and psychological interventions aimed at prevention and treatment of these destructive and often deadly maladies.
The scientists conducting the present study found that subjects with a family history of alcohol use disorders (family history-positive or FHN) exhibited a different physiological response to the expectation of drinking an alcoholic beverage than subjects whose families did not have this history (family history-negative or FHN). Specifically, the FHP subjects appeared to produce more of the neurotransmitter dopamine when presented with an opportunity to drink than the other participants in the study, including those already diagnosed with an alcohol use disorder.
The brain’s dopamine system is a key reward pathway in the brain. and the way in which we experience physiological rewards is essential to our ability to learn new things. Receiving a reward teaches us teach us to repeat the behaviors that earned us the reward. As Dr. Martha Burns of Northwestern University explained, dopamine is the “save button” in the brain: “When dopamine is present during an event or experience, we remember it; when it is absent, nothing seems to stick.” All psychoactive substances raise levels of dopamine in the brain. This is why the mesolimbic dopamine system is considered essential to the development and progression of compulsive drug and alcohol use.
The strategy in this study was to examine the release of dopamine in 3 groups of subjects who consumed both alcohol and a placebo beverage that smelled like alcohol. One group of subjects consisted of people diagnosed with an alcohol use disorder and the other two groups consisted of healthy subjects (moderate drinkers who would be able to tolerate the alcohol introduced in the experiment) with family histories that were either positive or negative for a family history of alcohol. Positron Emission Tomography imaging was used to trace the release of dopamine in the brains of study subjects, and each subject received 2 PET scans at least 2 weeks apart. Participants who received the placebo drink during their initial scan received the alcoholic beverage during the subsequent scan and vice-versa. Participants were told this was to be the procedure and all participants were able to identify which beverage they received after consuming it.
The PET scans found, as expected, “a highly significant (dopamine)-releasing effect of alcohol compared with placebo across all participants”, particularly in the ventral striatum, a region of the brain that plays a critical role in acquiring and developing reward-based behaviors. However, participants with a family history of alcohol use disorders exhibited signs of greater dopamine release prior to drinking the alcoholic beverage when they had received a placebo drink during their first experimental session. Remember, all participants were able to identify which beverage they had consumed, so everyone knew, prior to the second session, whether or not they would be consuming an alcoholic drink. So heightened dopamine activity in the FHP subjects before receiving the second drink is an indication that they were anticipating the reward to come, and their brains were significantly more activated by this expectation than the brains of other study subjects. Even participants already diagnosed with alcohol use disorders were not as activated as the FHP subjects. The researchers speculated that this powerful response to the expectation of consuming alcohol could represent an important risk factor for the development of a substance disorder in the future.
This is important information for people who grow up in families where substance use disorders are prevalent and who are considering their own risk for developing a serious problem. It is also an important finding to think about if you find yourself judging the character or motives of people in your life whose drug and alcohol-related behaviors have hurt you. People with these disorders cause real pain to their families and friends and of course their destructive acts feel personal, but I think the words of Dr. Michael Miller, the past president of the American Society of Addiction Medicine are helpful to consider:
At its core, addiction isn’t just a social problem or a moral problem or a criminal problem. It’s a brain problem whose behaviors manifest in all these other areas. Many behaviors driven by addiction are real problems and sometimes criminal acts. But the disease is about brains, not drugs. It’s about underlying neurology, not outward actions (emphasis mine)“
For more about the neurobiology of substance use disorders, please read Where Is That Pink Cloud When You Need It? elsewhere on my blog. If you would like to read more about the impact of substance use disorders on the family, try Nurse Jackie Takes Us to Hell and Back: Was This Relapse Necessary?
Dr. Wood is the author of Raising Healthy Children in an Alcoholic Home and Children of Alcoholism: The Struggle for Self and Intimacy in Adult Life.