New genetic links between cannabis use and brain function
Researchers are shedding light on why people respond to cannabis in different ways. In one of the largest studies of its kind, scientists from the University of California, San Diego, and the DNA testing service 23andMe analyzed genetic data from more than 130,000 participants who reported their cannabis use and provided DNA samples. The results, published in Molecular Psychiatry, suggest that certain genes may influence not only whether someone tries cannabis but also how often they use it and whether their use could escalate into problematic use.
The study emphasizes that cannabis behavior exists on a continuum. It also notes that genetics interact with environment, lifestyle, and personal choices, making it unlikely that a single gene determines outcomes. Still, mapping these genetic pathways could help public health efforts tailor prevention and intervention strategies to those most at risk.
Two major genetic players emerge
Using a genome-wide association approach (GWAS), the researchers identified two major genetic players tied to lifetime cannabis use and patterns of use. The first is Cell Adhesion Molecule 2 (CADM2), a gene involved in how brain cells communicate. CADM2 has previously been linked to impulsivity, obesity, and cancer risk, suggesting it may influence how people weigh immediate rewards, including drug use, against long-term goals.
The second gene is Metabotropic Glutamate Receptor 3 (GRM3), which impacts brain plasticity and has associations with psychiatric conditions such as schizophrenia and bipolar disorder. The GRM3 link points to how the brain’s adaptability to new experiences could modulate responses to cannabis, potentially affecting both use frequency and vulnerability to mental health symptoms.
Beyond these two genes, the study uncovered 40 additional genes associated with lifetime cannabis use and four more connected to how often people use cannabis. Notably, 29 of these genes were previously unknown in cannabis research, underscoring how much there is still to learn about the genetic architecture of drug use.
Genetic overlap with other traits
When the researchers compared cannabis-related genes with data from two major US health databases, they found significant overlap with more than 100 traits. These include attention-deficit/hyperactivity disorder (ADHD), anxiety, depression, and risk-taking behaviors. The genetic links also extended to certain physical health conditions, such as diabetes and chronic pain, and even to infectious diseases like HIV and hepatitis, illustrating the broad network of biological pathways that can intersect with cannabis use.
What this means for prevention and treatment
Dr. Sandra Sanchez-Roige, professor of psychiatry at UC San Diego and the study’s lead, emphasizes that possessing a risk-related gene does not doom someone to addiction. Environmental factors, social context, and individual choices remain decisive. The researchers stress that tagging intermediate traits—how people respond to cannabis before addiction may develop—could help identify who is at higher risk and when to intervene.
“Understanding the genetics of early-stage behaviours may help clarify who is at greater risk, opening the door to prevention and intervention strategies,” Sanchez-Roige said. Dr. Hayley Thorpe, a co-author, adds that genetic risk unfolds across stages, providing a roadmap for future research into targeted treatments and prevention programs.
Global context and future directions
Cannabis use is on the rise globally. In Europe, about 8.4% of adults aged 15 to 64 reported cannabis use in the past year, with daily or near-daily use at around 1.5%. Worldwide, the World Health Organization estimates roughly 147 million people use cannabis, about 2.5% of the global population. The researchers caution against deterministic interpretations: genetics contribute to risk, but the environment remains powerful in shaping outcomes.
As science advances, the hope is that genetic insights will inform more precise public health messages and personalized interventions. The long-term health effects of cannabis continue to be studied, and understanding genetic risk may be a valuable piece of the puzzle in reducing cannabis-related harm.
