Summary: A massive study of over 2.2 million individuals has fundamentally redefined how we understand the genetics of addiction. The research reveals that most genetic risk for substance use disorders (SUD) isn’t about how the body reacts to a specific drug, but how the brain is “wired” for behavioral disinhibition.
By analyzing alcohol, tobacco, cannabis, and opioid use together, researchers identified that a broad “externalizing” pathway—linked to reward processing and impulse control—is the primary driver of addiction across the board.
Key Facts & Statistics
- The 2.2 Million Cohort: This is one of the largest genomic analyses of its kind, pooling data to tease apart shared versus substance-specific genetic roots.
- The Two-Pathway Model:
- Broad Externalizing Pathway: Genes that affect reward processing, self-control, and risk-taking. This pathway also links to ADHD, conduct problems, and impulsivity.
- Substance-Specific Pathways: Narrower genetic factors, such as how the body metabolizes alcohol or how nicotine receptors in the brain respond to tobacco.
- Brain vs. Body: Senior author Danielle Dick notes that addiction risk is mostly about brain wiring (how we weigh consequences) rather than “biological response” (how the body breaks down a substance).
- Neural Plasticity: Many of the “broad liability” genes are involved in brain signaling and neural plasticity, suggesting the brain’s ability to adapt to rewards is a central risk factor.
- Polygenic Power: Researchers created “polygenic scores” that can predict a person’s general vulnerability to any addiction, while specific scores can pinpoint risks for a single drug like nicotine.
Source: Rutgers University
Most of the genetic risk for developing a substance use disorder comes from genes that broadly affect how our brains process rewards, regulate impulses and weigh consequences – not from genes that specifically influence substance use disorder or any single drug.
Researchers of a Rutgers Health–led study headed by Holly Poore, a faculty instructor of psychiatry at Rutgers Robert Wood Johnson Medical School, analyzed genetic data from previously published genome-wide association studies totaling more than 2.2 million individuals to understand how genes shape vulnerability to alcohol, tobacco, cannabis and opioid use disorders.
According to the study published in Nature Mental Health, members of the team found genetic risk operates along two main pathways:
- A broad “behavioral disinhibition” or externalizing pathway, which involves brain systems for reward processing, self-control and risk-taking. Externalizing refers to a heritable pattern of behaviors characterized by difficulty regulating impulses and actions such as impulsivity, attention-deficit/hyperactivity disorder (ADHD), conduct problems and risk-taking behaviors. This pathway cuts across many forms of addiction and related behavioral outcomes.
- Substance-specific pathways that are more narrowly tied to particular drugs (for example, genes involved in alcohol metabolism or nicotine receptors).
“Most of the genetic predisposition to substance use disorders isn’t about how bodies respond to drugs; it’s about how brains are wired,” said Danielle Dick, director of the Rutgers Addiction Research Center within the Rutgers Brain Health Institute and senior author of the study.
“Specifically, risk is mostly related to genes that broadly impact how our brains process rewards and regulate behavior.”
Dick added, “Those same genes show up across many outcomes – things like ADHD, conduct problems and other risky behaviors – and then layered on top of that are genes that are more specific to each substance. What this paper does, for the first time, is tease apart those pathways at the genomic level.”
Using advanced genomic methods, the researchers analyzed four substance use disorders –alcohol, tobacco, cannabis and opioids – together with related externalizing traits such as ADHD, risk-taking and initiation of substance use. This approach allowed them to identify hundreds of genetic variants associated with a broad externalizing liability as well as genes that were more specific to particular substances.
The researchers found that modeling addiction together with these other traits greatly increased their ability to detect genetic effects without sacrificing the means to see substance-specific signals.
Many of the genes linked to the broad liability were involved in brain signaling, reward processing and neural plasticity, while substance-specific genes mapped onto pathways such as alcohol metabolism or nicotinic acetylcholine receptors implicated in tobacco use.
“Traditionally, gene-finding efforts have focused on one disorder at a time,” said Poore, noting how one genome-wide association study is for alcohol, another for tobacco, etc.
“But substance use disorders almost never occur in isolation, and decades of twin and family studies have shown that they share a lot of their genetic roots with each other and with other externalizing conditions.
“By modeling that shared genetic architecture directly, we were able to discover more about both the broad and specific biological pathways that contribute to addiction.”
The researchers also used these genomic discoveries to build polygenic scores, summary measures that combine thousands of genetic variants into a single index of genetic liability. Broad externalizing polygenic scores were especially powerful in predicting risk for multiple substance use disorders, while substance-specific scores provided more precise information about vulnerability to specific drugs, such as alcohol or nicotine.
“From a translational perspective, we can start to think about genetic risk on two levels,” Dick said.
“A broader metric can tell us who is generally more vulnerable to addiction and other externalizing problems, while more specific scores can help us understand who is at higher risk for problems with different substances.
“That doesn’t mean genes determine someone’s destiny, but they can help us identify who might benefit most from targeted prevention or earlier intervention. Genetic risk scores may also help us develop more individualized treatments and recovery plans.”
In addition to mapping genetic risk pathways, the researchers conducted network and drug-target analyses that pointed to potential biological systems and medications that could be leveraged or repurposed for treatment. Many of the genes identified for the broad externalizing pathway overlapped with those implicated in other psychiatric and substance-related disorders, underscoring the shared biology across conditions.
The authors said their analyses were limited to individuals of European ancestry, reflecting the current availability of large-scale genetic datasets, and emphasize the urgent need for more diverse genomic research to ensure findings are relevant and equitable across populations.
“Addiction is incredibly complex, and this study shows just how important it is to look beyond any single substance or single gene,” Poore said.
“By understanding the common genetic roots that link substance use disorders with other forms of behavioral disinhibition – as well as the pathways that are specific to alcohol, nicotine, cannabis or opioids – we can build a more complete picture of vulnerability and ultimately support better prevention, intervention and treatment strategies.”
Funding: The study was co-authored by an international team of researchers from SUNY Downstate Health Sciences University, the University of California San Diego, Massachusetts General Hospital and Harvard Medical School, Washington University School of Medicine, Emory University, the University of Texas at Austin, Vanderbilt University Medical Center and collaborators from the Collaborative Study on the Genetics of Alcoholism, among others.
Key Questions Answered:
A: Not at all. It means they share a genetic architecture related to impulse control. Genes provide a “vulnerability map,” not a destiny. Knowing this allows for targeted prevention—if we know a child has high genetic “disinhibition,” we can provide extra support for self-regulation skills early on to lower their risk of ever starting substance use.
A: This is where the layered approach comes in. Think of the broad genes as the “foundation” of a house and the substance-specific genes as the “decor.” Everyone at risk has the same shaky foundation (impulsivity), but their specific biology—like having highly sensitive nicotine receptors—might determine which “room” in the house they end up stuck in.
A: Yes. By identifying the genes in the broad externalizing pathway, scientists can look for medications that strengthen the brain’s “brakes” or normalize reward signaling. Instead of a drug just for “quitting smoking,” we might develop treatments that help the brain regulate impulses across all areas of life.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this genetics and addiction research news
Author: Patti Zielinski
Source: Rutgers University
Contact: Patti Zielinski – Rutgers University
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Multivariate genetic analyses of 2.2 million individuals reveal broad and substance-specific pathways of addiction risk” by Holly E. Poore, Chris Chatzinakos, Brittany Leger, Jean Gonzalez, Travis T. Mallard, Fazil Aliev, Alexander Hatoum, Irwin D. Waldman, Sandra Sanchez-Roige, Abraham A. Palmer, K. Paige Harden, Danielle M. Dick & Peter B. Barr. Nature Mental Health
DOI:10.1038/s44220-026-00608-6
Abstract
Multivariate genetic analyses of 2.2 million individuals reveal broad and substance-specific pathways of addiction risk
Ongoing efforts to identify genes involved in substance use disorders (SUDs) often focus on individual disorders despite high rates of co-occurrence with each other and other externalizing traits.
Here we investigate whether incorporating data on other externalizing traits can boost power to detect without sacrificing specificity of SUD genetic signal. We used multivariate genomic analyses and downstream biological annotation and genetic association analyses to explore this question.
We found that joint analysis of SUDs and other externalizing traits resulted in increased insights into the neurobiology of broad and substance-specific SUD risk. We found no evidence of loss of specificity for SUD genetic signal but note improvements in our ability to characterize the neurobiology of broad and substance-specific SUD genetic effects.
Our findings suggest that genetic risk for SUDs operates largely via pathways shared with other behaviors characterized by behavioral disinhibition, with additional substance-specific risk, and that modeling this shared disposition improves gene discovery.
