A multivariate genetic analysis of 2.2 million people indicates that the tendency toward substance use disorders (SUDs) is largely independent of the substance of abuse. The findings add further weight to A Unified Theory of Addiction, which suggests a common mechanism behind both chemical and behavioral addictions.

Two Rutgers University professors are the corresponding authors for a team of over a dozen psychiatric researchers stretching from Boston to San Diego. The study was led by Dr. Holly Poore, a professor at Rutgers University Robert Wood Johnson Medical School, and supervised by Dr. Danielle Dick, director of the Rutgers Addiction Research Center.

The researchers used a variety of ingenious methods for incorporating the co-occurrence of addictions, as well as “other externalizing traits,” including age of substance initiation and diagnosis of attention deficit hyperactivity disorder (ADHD). They find a much stronger genetic relationship between behavioral and substance addictions than for any individual substance or behavior.

Substances included in the study are:

• problematic alcohol use (PAU)
• problematic tobacco use (PTU)
• opioid use disorder (OUD)
• cannabis use disorder (CUD)

The externalizing factors they analyzed are:

• ADHD
• age of cannabis initiation
• age of smoking initiation
• age at first sexual intercourse
• number of sexual partners
• risk-taking propensity

And the bottom line conclusion they reached:

Our findings suggest that genetic risk for SUDs operates largely via pathways shared with other behaviors characterized by behavioral disinhibition…

The authors more clearly spell out the significance of the genetic commonality between behavioral disorders and SUDs:

If SUD genetic risk largely reflects broad externalizing risk, it suggests that individuals at risk for or currently experiencing an SUD are also at risk for other externalizing problems, which should be taken into account in prevention and intervention efforts.

The researchers write that the genetic risk of getting an SUD “can be conceptualized as a combination of risk for behavioral disinhibition and physiological response to the individual substance.”

In an interview about the study for Newswise, Dr. Dick adds some nuance to the implications of the analysis: “Most of the genetic predisposition to substance use disorders isn’t about how bodies respond to drugs; it’s about how brains are wired. Specifically, risk is mostly related to genes that broadly impact how our brains process rewards and regulate behavior.”

Dr. Poore explained to Newswise that previous studies searching for the genetic origins of SUDs focused on a single substance, whereas data shows that co-occurrence is common. The ability to look at all these SUDs at once reveals a “common pathway” between all substances of abuse and behavioral disorders.

Newswise summarized what the massive study reveals: “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 shared biology across conditions” sounds a lot like A Unified Theory of Addiction, written by Dr. Robert Pretlow, publisher of AddictionNews. His paper assembles the evidence for a displacement mechanism that uses substances of abuse and compulsive behaviors to mitigate stress. This is the first multivariate genetic analysis that indicates a unified genetic source between all addictive behaviors, an important milestone in understanding and treating all disorders by targeting a shared pathway.

Written by Steve O’Keefe. First published March 25, 2026.

Sources:

“Multivariate genetic analyses of 2.2 million individuals reveal broad and substance-specific pathways of addiction risk,” Nature Mental Health, March 20, 2026.

“Genes Tied to Impulse Control Play a Major Role in Addiction Risk,” Newswise, March 20, 2026.

Image Copyright: ilyakalinin.