Genes that influence cannabis use and addiction finally identified

Cannabis is everywhere now – from casual use to medical treatment. Yet one question stays unsolved: why does it pull some people deeper than others?

A team at the University of California San Diego School of Medicine, in partnership with 23andMe, tried to find that answer in our DNA.

The study, published in Molecular Psychiatry, reveals genes tied to cannabis use and its ripple effects on mental and physical health.

Genes shape cannabis use

“Cannabis is widely used, but its long-term effects on health remain poorly characterized,” said Dr. Sandra Sanchez-Roige, associate professor of psychiatry at UC San Diego School of Medicine and senior author of the study.

Her team looked at how genes might push some people closer to cannabis use disorder – a condition that can quietly disrupt work, focus, and daily life.

“While most people who try cannabis do not go on to develop cannabis use disorder, some studies estimate that nearly 30% will,” said Dr. Sanchez-Roige.

“Understanding the genetics of early-stage behaviors may help clarify who is at greater risk, opening the door to prevention and intervention strategies.”

The research didn’t aim to judge use. The goal was to uncover the biological roots that shape behavior long before a person realizes it.

Linking genes and cannabis use

The study used a genome-wide association approach – GWAS, as scientists call it. The method compares bits of DNA across thousands of people to spot common threads.

More than 131,000 23andMe participants took part. Each one answered simple questions: have you ever tried cannabis, and if yes, how often?

“We’ve known for decades that genetic factors influence whether or not people will try drugs, how frequently they use those drugs, and the risk that they will become addicted to them,” said Dr. Abraham A. Palmer, professor and vice chair for basic research at UC San Diego.

“Genetic tools like GWAS help us identify the molecular systems that connect cannabis use to brain function and behavior.”

The scale of the study gave the team something rare – clarity. It showed that cannabis use is not random. Certain genes quietly guide how curiosity turns into habit.

Key genes identified

The first major gene spotted was CADM2. It helps nerve cells connect and talk to each other.

Earlier work linked CADM2 to impulsive behavior, obesity, and even cancer spread. The study found this gene tied to both lifetime cannabis use and how often people used the drug.

The second was GRM3, a gene that controls how neurons communicate and adapt. This one has known ties to mental health conditions such as schizophrenia and bipolar disorder.

“We showed that the genetics of cannabis use – both trying it and using it more often – are tied to the genetics of other psychiatric traits, cognitive measures, and even physical health problems,” said Dr. Sanchez-Roige.

The two genes didn’t act alone. They pointed toward entire systems in the brain that influence reward, curiosity, and control – the mix that shapes human behavior.

Genetic nudges toward cannabis use

Digging deeper, the team uncovered 40 other genes linked to lifetime cannabis use and four connected to frequency.

Twenty-nine of these had never before been associated with cannabis in any study. Each one added another piece to the puzzle – a hint that cannabis use depends on many small genetic nudges rather than one big trigger.

Some genes affect how people handle stress. Others may change how the brain weighs risk and reward. Together, they trace a network where biology and behavior constantly interact.

Health connections in the genome

To see what these genes meant for overall health, the researchers compared them against data from the National Institutes of Health’s All of Us Research Program and Vanderbilt University’s biobank. The overlaps were striking.

People with genetic markers for cannabis use also showed higher risks for ADHD, depression, and anxiety. Some scored differently on measures of decision-making and impulse control.

Physical health links appeared too – diabetes, chronic pain, and heart disease. The same genetic tendencies also overlapped with tobacco use and certain infectious and autoimmune diseases.

The data suggested something larger: cannabis use isn’t an isolated habit. It fits within a broader biological pattern that links body, brain, and behavior.

Catching risk early

Study first author Dr. Hayley Thorpe is a visiting scholar in Dr. Sanchez-Roige’s lab and postdoctoral researcher at Western University.

“Cannabis use exists on a continuum,” said Dr. Thorpe. “By studying these intermediate traits, we can begin to map how genetic risk unfolds before cannabis use disorder develops.”

Her words hint at a practical goal – catching risk early. If genetic signs can predict vulnerability, prevention doesn’t have to wait until addiction becomes visible.

The bigger picture

There are still no FDA-approved medications for cannabis use disorder. Treatment relies mostly on therapy, not biology. The researchers hope their findings can change that, turning genes into clues for new therapies and early intervention.

The research adds to a growing view of addiction as part biology, part behavior. It’s not just about choice or exposure. It’s also about how the brain’s wiring reacts when curiosity meets chemistry.

This study shifts the conversation around cannabis. Instead of moral debates, it focuses on science – the kind that explains why some people are more vulnerable than others.

By connecting genes to cannabis behavior, the UC San Diego and 23andMe team has created a map of risk and resilience. It’s a reminder that understanding addiction starts with understanding ourselves, right down to the code that makes us who we are.

The study is published in the journal Molecular Psychiatry.

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