Specific genes appear to influence whether people try cannabis and their susceptibility to cannabis addiction.
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Your DNA could hold more clues about your relationship with cannabis than you may think.
In one of the largest studies of its kind, researchers from the University of California, San Diego and DNA testing service 23andMe identified specific genes linked to cannabis use – and found that those same genes are tied to mental health conditions, cognitive traits, and even physical illnesses.
Published in the journalMolecular Psychiatry, the study suggests that the way people's brains respond to cannabis could be partly written in their genetic codes, influencing not only whether they try the drug, but how often they use it and whether that habit veers into an addiction.
“Cannabis is widely used, but its long-term effects on health remain poorly characterised,” said Dr Sandra Sanchez-Roige, an associate professor of psychiatry at UC San Diego and the research leader.
Estimates suggest nearly 30 per cent of people who try cannabis go on to develop cannabis use disorder, Sanchez-Roige said.
"Understanding the genetics of early-stage behaviours may help clarify who is at greater risk, opening the door to prevention and intervention strategies," she added.
The researchers hope that uncovering the genetic pathways involved in cannabis addiction could eventually lead them to targeted treatments and preventive efforts.
A genetic map of cannabis behaviours
Sanchez-Roige's team analysed data from more than 130,000 participants who reported their cannabis use and provided DNA samples. Using a genome-wide association study, or GWAS, the researchers uncovered two major genetic players.
The first, Cell Adhesion Molecule 2 (CADM2), helps brain cells communicate and has previously been linked to impulsivity, obesity, and cancer risk.
The other, Metabotropic Glutamate Receptor 3 (GRM3), influences brain plasticity and is associated with psychiatric disorders such as schizophrenia and bipolar disorder.
The researchers also identified 40 additional genes linked to lifetime cannabis use and four connected to how frequently people use the drug, 29 of which were previously unknown in cannabis research.
When compared with two major US health databases, the findings revealed striking genetic overlaps.
Cannabis-related genes were associated with more than 100 traits, including attention-deficit/hyperactivity disorder (ADHD), anxiety, depression, andrisky behaviours, as well as physical conditions such as diabetes and chronic pain, the study found.
The genes also correlated with an increased risk of tobacco use, autoimmune disorders, and infectious diseases such as HIV and hepatitis.
Notably, while having certain genes may increase people's susceptibility to cannabis use or related disorders, they do not directly determine whether someone will develop a problem. Environment, lifestyle, and personal choices still play a key role.
“By studying these intermediate traits, we can begin to map how genetic risk unfolds before cannabis use disorder develops," said Dr Hayley Thorpe, a postdoctoral researcher at Western University and one of the study's authors.
The findings come amid rising rates of cannabis use globally.
In Europe, an estimated 8.4 per cent of adults aged 15 to 64 reported using cannabis in the past year, equating to about 24 million people. Among them, 1.5 per cent were daily or almost daily users.
Globally, about 147 million people – 2.5 per cent of the population – use cannabis, according to the World Health Organization (WHO).
“Cannabis use exists on a continuum,” Thorpe said.
