Two significant studies published this month have reignited concerns about cannabis and its impact on mental health, particularly amongst vulnerable populations. The research challenges the benign image cultivated by pro-legalisation advocates and raises urgent questions about public health policy.

Cannabis Psychosis Link Strengthened by Latest Evidence

A study in JAMA Psychiatry has revealed that cannabis use amongst people with psychosis increased nearly 10% following legalisation. This finding sits at a troubling crossroads between public health and safety, demonstrating that those most psychologically vulnerable are also most susceptible to policy changes that normalise the drug.

The research reinforces more than a decade of evidence showing legalisation lowers risk perception and drives higher consumption. The conclusion is stark: cannabis can trigger psychotic episodes, and those episodes carry consequences far beyond individual users.

Meanwhile, researchers at the University of California San Diego, collaborating with genetic testing company 23andMe, have identified specific regions of the human genome associated with cannabis use. Their genome-wide association study analysed data from 131,895 participants, uncovering new relationships between genetic variants and psychiatric, cognitive, and physical health.

The Genetic Dimension of Cannabis Risk

The UC San Diego research, published in Molecular Psychiatry, found that lifetime cannabis use was associated with two key genes. The first, Cell Adhesion Molecule 2 (CADM2), involves cell assembly and signalling between nerve cells, particularly in the brain. Previous studies have linked CADM2 to impulsive personality traits, obesity, and cancer metastasis.

The second gene, Metabotropic Glutamate Receptor 3 (GRM3), plays a role in communication between neurons and long-term brain plasticity. GRM3 has already been connected to psychiatric disorders including schizophrenia and bipolar disorder.

Dr Sandra Sanchez-Roige, associate professor of psychiatry at UC San Diego and senior author of the study, explained: “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.”

A secondary analysis revealed an additional 40 genes associated with lifetime cannabis use and four genes linked to frequency of use. Twenty-nine of these genes had not previously been associated with cannabis-related traits.

Over 100 Health Conditions Connected to Cannabis Use

When researchers analysed which health conditions correlated with genetic predisposition for cannabis use, the results proved extensive. Using data from the National Institutes of Health’s All of Us Research Programme and Vanderbilt University Medical Center’s biobank, they identified genetic correlations with more than 100 different traits.

These included psychiatric conditions such as schizophrenia, ADHD, anxiety, and depression. Cognitive traits like executive function and risk-taking behaviour also showed correlations. Physical health problems ranging from diabetes and chronic pain to coronary artery disease appeared in the data.

The cannabis psychosis link emerged particularly strongly, with increased risk for tobacco use, infectious diseases including HIV and viral hepatitis, and various autoimmune conditions.

Dr Abraham Palmer, professor and vice chair for basic research in psychiatry at UC San Diego, noted: “We’ve known for decades that genetic factors influence whether people will try drugs, how frequently they use them, and the risk they’ll become addicted. Genetic tools like genome-wide association studies help us identify the molecular systems connecting cannabis use to brain function and behaviour.”

Understanding Cannabis Use Disorder

Not everyone who tries cannabis develops problems, but the risks are significant. Some studies estimate nearly 30% of users will develop cannabis use disorder, which can seriously interfere with daily life.

Dr Hayley Thorpe, first author of the genetic study and postdoctoral researcher at Western University, explained: “Cannabis use exists on a continuum. By studying these intermediate traits, we can begin to map how genetic risk unfolds before cannabis use disorder develops.”

The research represents one of the first genome-wide association studies examining behaviours that precede cannabis use disorder. Understanding the genetics of early-stage behaviours may help clarify who faces greater risk, potentially opening doors for prevention and intervention strategies.

Currently, no FDA-approved drug therapies exist to treat cannabis use disorder. Researchers hope their biological discoveries will support future efforts to identify therapeutic targets and preventative interventions.

Why Legalisation Has Increased Vulnerability

The JAMA Psychiatry findings carry particular weight because they demonstrate how policy changes affect the most vulnerable. Those experiencing psychological distress often turn to cannabis for relief, encouraged by marketing that systematically downplays risks.

Major shifts in policy began in the 1990s with the rise of “medical” cannabis, as the industry persuaded much of the public and many lawmakers that the drug was not only harmless but beneficial. That narrative has fostered a culture of denial amongst advocates who refuse to acknowledge mounting research linking cannabis to serious health risks.

The industry built its campaign for liberalisation on misinformation about the drug’s harms, using that narrative to push through ballot measures and legislation for recreational use throughout the 2010s. What began as victories in states like Colorado and California has since stalled, however. Cannabis legalisation has been defeated in seven of the last 10 state initiatives in America.

Public Opinion Shifts as Evidence Mounts

The tide appears to be turning. A recent Gallup poll showed a 10-point reduction between 2022 and 2024 in the number of Americans who thought cannabis had a positive effect on users, dropping from 53% to 43%.

This declining support likely reflects growing public recognition of the drug’s harms. Legalisation and commercialisation have normalised use, and vulnerable populations are visibly paying the price. Advocates once promised legalisation would pose no threat to public health, yet both new research and lived experience tell a different story.

Study after study confirms that increased cannabis use, particularly beginning in adolescence, makes it far more likely someone will develop schizophrenia or another form of psychosis. The cannabis psychosis link proves especially concerning because those at highest risk often face the strongest marketing pressures.

The Industry’s Incentive Problem

Without stronger accountability measures, transparency from the cannabis industry remains unlikely. Clear health warnings and potency limits in legal jurisdictions could help, but the industry has little incentive to implement them voluntarily.

Marketing continues to downplay risks, particularly around heavy use and high-potency products. The segment of the population most psychologically vulnerable to cannabis — both in using it and reacting to it — also proves most vulnerable to legalisation’s normalising effects.

What the Evidence Demands

These findings arrive at a moment when policymakers worldwide are reconsidering cannabis policy. The research doesn’t support prohibition as the sole answer, but it does demand honest reckoning with the drug’s risks.

Dr Sanchez-Roige emphasised: “Cannabis is widely used, but its long-term effects on health remain poorly characterised. Understanding the genetics may help clarify who is at greater risk.”

The genetic research opens possibilities for identifying those most vulnerable before problems develop. Combined with the JAMA Psychiatry findings about post-legalisation increases in use amongst people with psychosis, a picture emerges of policy changes that have failed to protect public health.

Moving Forward: Policy and Prevention

Policymakers should treat cannabis as a serious public health issue requiring stronger regulation where it’s legal, honest messaging about risks, and willingness to confront uncomfortable truths about legalisation’s consequences.

Where cannabis is legal, jurisdictions need clear health warnings on products, potency limits to reduce high-THC exposure, marketing restrictions protecting vulnerable populations, and funding for treatment programmes. Public education campaigns based on current scientific evidence are essential.

The connection between cannabis use and psychosis isn’t speculation. It’s documented across multiple studies using different methodologies. The genetic research adds biological mechanisms to epidemiological findings, whilst the JAMA Psychiatry study demonstrates real-world policy impacts.

For those genetically predisposed to psychiatric conditions, for adolescents whose brains are still developing, for people experiencing psychological distress who turn to cannabis seeking relief — the stakes couldn’t be higher. The science has spoken. Now it’s time to listen.

Source: dbrecoveryresources