About 30% of people who have ever tried cannabis eventually develop a dependence on the substance. The main risk factors include frequency of use and a family history of drug use.

Recent studies have enabled scientists to identify specific regions of the human genome associated with cannabis use. This suggests that a predisposition to marijuana addiction may be partially encoded in our DNA.

A study conducted by the University of California San Diego (UCSD) School of Medicine in collaboration with 23andMe, a company specializing in genetic testing, involved nearly 132,000 participants from the 23andMe platform. Participants completed a survey about their cannabis use and provided their genetic data.

Genome-Wide Association Studies

This type of research is known as a genome-wide association study (GWAS). Its essence lies in comparing the DNA of thousands of people to find genetic variations that are more common among individuals with certain traits or conditions. GWAS allows researchers to identify genetic differences linked to diseases, behavioral traits, or physical characteristics.

Previously, GWAS have helped establish a causal link between gut bacteria and insomnia, identify nearly 300 genetic variants contributing to depression, and create a genetic map of age-related decline in resilience among people over 65.

Key Genes and Their Significance

An article published in the journal Molecular Psychiatry highlighted two key genes associated with lifetime cannabis use and several other conditions. The first is the cell adhesion molecule 2 (CADM2), previously linked to impulsivity, obesity, and cancer metastasis. The second is the metabotropic glutamate receptor 3 (GRM3), which has been associated with schizophrenia and bipolar disorder. However, the presence of these genes does not mean that cannabis use will necessarily lead to the development of these diseases—it only points to possible shared biological mechanisms.

Further analysis identified 40 more genes linked to lifetime cannabis use and four genes influencing frequency of use.

Genetics and Addiction Risk

“We have shown that the genetics of cannabis use—both first-time use and more frequent consumption—are connected to the genetics of other psychiatric traits, cognitive indicators, and even some physical health problems,” noted senior study author Sandra Sanchez-Roige. According to her, understanding the genetics of early behavioral stages can help identify people at risk and pave the way for prevention and early intervention.

The Relevance of the Problem

In the United States, marijuana is legal in 24 states, and according to a 2024 report from the Substance Abuse and Mental Health Services Administration, 20.6 million people in the country have experienced a disorder related to marijuana use. This condition is characterized by significant impairment or distress due to problematic substance use, and the number of such cases has slightly increased compared to previous years. Currently, there are no FDA-approved medications for treating cannabis dependence.

Research Prospects

While having certain genes does not guarantee the development of addiction, understanding the genetic and molecular mechanisms linking the brain and substance use can help identify individuals with increased susceptibility and provide them with support at early stages. “By studying these intermediate traits, we can begin to map how genetic risk manifests before the onset of cannabis use disorder,” emphasized lead study author Hayley Thorpe from Western University.