DNA and cannabis: what a new study reveals
Researchers have long asked how much our choices around cannabis are shaped by biology versus environment. A landmark study from the University of California, San Diego, in collaboration with DNA testing service 23andMe, provides fresh evidence that genetics play a meaningful role in cannabis use, how often people use it, and the risk of developing related disorders. Published in Molecular Psychiatry, the work analyzes data from more than 130,000 participants who reported their cannabis use and donated DNA samples.
Two key genetic players and what they do
The researchers identified two major genetic players linked to lifetime cannabis use. The first is CADM2 (Cell Adhesion Molecule 2), a gene involved in how brain cells communicate. CADM2 has previously been associated with impulsivity, obesity, and cancer risk, and now with patterns of cannabis use. The second is GRM3 (Metabotropic Glutamate Receptor 3), which influences brain plasticity and has connections to psychiatric conditions such as schizophrenia and bipolar disorder. In all, the study found 40 additional genes tied to lifetime cannabis use and four linked to how frequently cannabis is used, 29 of which were previously unknown in cannabis research.
How genetics intersect with health and behavior
Comparing cannabis-related genes with large US health databases unveiled overlaps with more than 100 traits. These include attention‑deficit/hyperactivity disorder (ADHD), anxiety, depression, and risky behaviors, as well as physical health conditions like diabetes and chronic pain. The findings also showed correlations with higher risks of tobacco use, autoimmune disorders, and infectious diseases such as HIV and hepatitis. Importantly, possessing certain genetic variants does not seal a fate: environment, lifestyle, and personal choices still play essential roles in whether someone uses cannabis and whether that use becomes problematic.
From genetic risk to prevention
As Dr. Sandra Sanchez-Roige notes, cannabis use is widespread, but its long‑term health effects are not fully characterized. The research aims to map how genetic risk unfolds before a cannabis use disorder might develop, opening the door to targeted prevention and interventions. Dr. Hayley Thorpe adds that studying these intermediate traits helps clarify why some individuals progress from first use to problematic use, and why others do not reach that stage.
Implications for clinicians and the public
The study emphasizes a continuum of cannabis use rather than a simple on/off threshold. This framing supports personalized approaches to prevention and treatment, particularly for those with elevated genetic risk combined with certain environmental factors. While the genetics provide clues, they are not destiny. Public health messages remain vital, including education about risks, mental health support, and access to evidence-based treatments for those who develop cannabis use disorders.
Global context and future directions
Cannabis use is rising in many regions. In Europe, about 8.4% of adults aged 15–64 reported cannabis use in the past year, translating to roughly 24 million people, with daily users constituting a smaller share. Worldwide, the World Health Organization estimates around 147 million people (2.5% of the population) use cannabis. Dr. Sanchez-Roige and colleagues argue that genetic insights, layered with environmental data, could guide prevention programs and, eventually, targeted therapies for addiction or related psychiatric conditions.
A cautious note on interpretation
Experts emphasize that genetic associations indicate risk, not certainty. The same gene can influence multiple traits, and its impact may vary across populations and life circumstances. Ongoing research will refine these links and help translate them into practical tools for individuals, families, and healthcare systems.
