Addiction Risk Genes Point to Brain Wiring, Not Just Substances

Scientists have analysed genetic data from more than 2.2 million people and found that addiction risk genes mostly shape how the brain regulates behaviour. The strongest inherited drivers of addiction are not about how the body processes alcohol, tobacco, cannabis or opioids. They are about how the brain manages reward, self-control and decision-making.

Researchers at Rutgers University published these findings in Nature Mental Health in March 2026. The study is one of the most comprehensive genetic investigations into substance use disorders ever conducted. Its findings carry real implications for prevention, early intervention and treatment.

What Addiction Risk Genes Actually Control

The study identified two distinct genetic pathways that shape vulnerability to substance use disorders.

The first is what researchers call the “behavioural disinhibition” pathway. This cluster of addiction risk genes governs the brain’s reward systems, self-control and decision-making. These genes also overlap with impulsivity, attention deficit hyperactivity disorder (ADHD), conduct problems and risk-taking tendencies. The same genetic architecture that drives risky or impulsive behaviour also underpins much of a person’s susceptibility to addiction.

The second pathway covers genes more specific to individual substances. These include genes affecting alcohol metabolism, such as variants in the ADH gene family, and nicotinic acetylcholine receptors tied to tobacco dependence. These substance-specific effects exist, but they play a comparatively smaller role in overall addiction vulnerability.

“Most of the genetic predisposition to substance use disorders is not about how bodies respond to drugs. It is about how brains are wired,” said Danielle Dick, director of the Rutgers Addiction Research Centre and the study’s senior author. “Risk is mostly related to genes that broadly impact how our brains process rewards and regulate behaviour.”

Why Studying Addiction in Isolation Has Held Science Back

For decades, researchers studied individual addictions in isolation. They examined alcohol use disorder separately from opioid use disorder. They treated tobacco dependence apart from cannabis use disorder. This study shows that approach leaves significant genetic signal undiscovered.

Substance use disorders almost never occur alone. Twin and family studies show they cluster together and share genetic roots with broader externalising conditions. The Rutgers team, led by Holly Poore, a faculty instructor of psychiatry at Rutgers Robert Wood Johnson Medical School, modelled four substance use disorders alongside related traits including ADHD, risk-taking and substance initiation behaviours simultaneously.

That joint approach paid off. The team identified 708 genomic risk loci in the combined externalising model. Of those, 187 (26%) were entirely new findings not seen in earlier genetic studies. A further 403 loci (57%) had no previous link to any substance use trait in the published literature.

“Substance use disorders almost never occur in isolation,” Poore said. “Decades of twin and family studies have shown they share genetic roots with each other and with other externalising conditions. Modelling that shared architecture helped us better understand both the common and substance-specific biology behind addiction.”

Genetic Risk for Addiction: What Polygenic Scores Reveal

Polygenic scores combine thousands of small genetic variants into a single estimate of risk. The researchers built these scores using data from two independent cohorts: the Collaborative Study on the Genetics of Alcoholism (COGA, N = 7,530) and the national All of Us cohort (up to 77,442 participants).

Broad polygenic scores from the externalising model predicted substance use disorders more accurately than narrower scores. In the All of Us cohort, the externalising polygenic score explained between 3.1% and 7.1% of the variance in substance use disorder diagnoses. Substance-specific scores worked better for pinpointing risk tied to a particular drug.

This two-level approach could reshape how clinicians think about prevention. A broad score captures general vulnerability to addiction. A substance-specific score then sharpens the picture. Together, they could help identify people who would benefit from earlier support before dependence develops.

The Implications for Prevention and Treatment

Understanding the genetic risk for addiction does not mean fatalism. Genes do not determine anyone’s destiny, as Dick was clear to note. But they do offer a clearer map of who may be at elevated risk and why.

For those working in public health, the findings highlight something important. Addressing addiction one substance at a time misses the shared biology underneath. Early intervention efforts that target impulsivity, reward-seeking and self-regulation may have far greater reach than those focused on a single drug. Research shows that SUDs are moderately heritable at 40 to 60%, meaning genetics plays a meaningful but not exclusive role in who develops these disorders.

The study also ran a drug repurposing analysis. By mapping identified genes onto the Drug-Gene Interaction Database, researchers found 118 druggable targets and over 1,000 FDA-approved drug-gene interactions in the externalising model alone. These included medications already used in addiction treatment: naltrexone, methadone, disulfiram, varenicline, baclofen and acamprosate. Existing treatments may work partly by acting on these shared genetic pathways.

A Note on Limitations

The entire analysis used genetic data from people of European ancestry. This reflects gaps in available data rather than a deliberate choice. It does mean the findings cannot yet be applied equally across all populations.

More diverse genomic research is urgently needed. Advances in our understanding of addiction risk genes must translate into tools and interventions that work for everyone, regardless of background.

What This Means Going Forward

Addiction science is moving towards a more joined-up view of human vulnerability. Rather than treating alcohol, opioids, tobacco and cannabis as entirely separate problems, the evidence now points to a common underlying genetic architecture. The brain’s capacity to regulate itself sits at the centre of it.

For policymakers, clinicians and those working in prevention, this shift matters greatly. Addiction risk genes are not the whole story. But they are an increasingly detailed and actionable part of it. Understanding them could guide more effective, personalised approaches to supporting people before problems take hold.

Source: dbrecoveryresources