It’s surprising that one of the most important questions in addiction science — Why do some people become addicted while others do not — remains relatively unexplored.

Of the adults in the U.S. who drink alcohol every day, only 12-15% are believed to have alcohol use disorder. That means 85% of those who consume alcohol every day do not suffer major problems as a result, although it may be harming their health.

Of the adults in the U.S. who eat every day, 3% have binge eating disorders, and 9% are considered severely obese. While the majority of American adults are overweight, more than 90% do not suffer from eating addiction when exposed to highly palatable foods.

What can we say about the common characteristics of those drinkers who become alcoholics and those eaters who become addicted to eating? Almost nothing. It is somewhat shocking that we know so little about what pushes people from casual use to compulsive use.

Dr. Donald W. Goodwin, chairman of the psychiatry department at the University of Kansas Medical Center, wrote that this question was “what I would most like to know” in his article on the causes of alcoholism for the British Journal of Addiction way back in 1979. The question remains largely unanswered today.

“The strongest predictor of alcoholism is a family history of alcoholism,” writes Dr. Goodwin, noting, “This does not mean alcoholism is inherited. Speaking French also runs in families.” Subsequent studies by Dr. George F. Koob and others have shown that alcoholism is heritable. Based on studies with twins, Dr. Koob and his colleagues reported:

The heritability of alcohol use disorders is estimated at approximately 50–60% of the total phenotypic variability.

The devil is in the details, however, as alcohol use disorders (AUD) are “highly heterogeneous making it a great challenge to define a specific universal set of genetic and environmental factors that influence risk across every population affected.” Along with Dr. Nora Volkow, director of the National Institute on Drug Abuse, Dr. Koob has identified three elements of addictive behavior:

1. binge/intoxication
2. withdrawal/negative affect
3. preoccupation/anticipation stages 

“After a period of repeated binge/intoxication, neuroadaptations occur leading to a negative emotional state (e.g., anxiety, depression, anhedonia)” as a result of withdrawal. So what is it that leads to a period of repeated binge/intoxication? If it is not genetics that causes some people to lose self-control, what is it?

A paper on the motivational processes underlying addiction published in the journal Current Topics in Behavioral Neurosciences tries to get us closer to those answers. The authors note that “not all drug-taking experiences will result in addiction, even if use is prolonged.” This very lengthy survey reviews numerous theories of how people become addicted, including:

• The hedonic allostasis model: overstimulation leading to reward deficiency
• The incentive sensitization model: transitioning from “like” to “must have”
• The addiction as disordered learning and decision-making model
• The impaired executive function model: prone to impulsive behavior

While all of these theories of addiction — many supported with studies conducted on rodents — help explain how the brain’s “reward system” can be hijacked by a substance or behavior, they don’t seem to ever answer the simple question: Do those who suffer from addiction have anything in common?

It turns out they DO have something in common, but very few researchers are willing to go there. The majority of people in treatment for substance use disorders in the U.S. are the victims of physical or sexual abuse. Not 3%. Not 9%. “More than half of substance abusers entering addiction treatment report a history of physical or sexual abuse,” say Harvard researchers.

Based on these numbers, I would suggest the first place to look for the causes of addiction is not inside the brains of mice but the backgrounds of abused human beings. What does trauma do to the human brain that makes it far more likely to become addicted? If trauma and its partner stress are what’s causing casual users to become compulsive users, shouldn’t more addiction research go into finding ways to mitigate chronic stress?

Nearly 50 years after Dr. Goodwin asked why some drinkers become alcoholics and some don’t, we have very few answers. Some of it is genetic, passed down through the family, and much of it appears related to adverse childhood experiences (ACEs). Do ACEs predispose people to addiction? Yes, say researchers, but they don’t know why. And so the search continues.

Written by Steve O’Keefe. First published June 12, 2026.

Sources:

“The Cause of Alcoholism and Why It Runs in Families,” British Journal of Addiction to Alcohol & Other Drugs, June 1979.

“Genetic studies of alcohol dependence in the context of the addiction cycle,” Neuropharmacology, August 1, 2017.

“Motivational Processes Underlying Substance Abuse Disorder,” Current Topics in Behavioral Neurosciences, January 1, 2017.

“Prevalence of physical and sexual abuse among substance abuse patients and impact on treatment outcomes,” Drug and Alcohol Dependence, April 4, 2005.

“Identifying connections between adverse childhood events and substance use disorders,” Penn Medicine, June 4, 2024.

Image Copyright: andreycherkasov.