Cannabis Research
Cannabis and Psychosis: Understanding the Real Risks
Cannabis has been part of human culture for thousands of years, valued not just for its recreational use but for its medicinal and spiritual purposes. Now, in recent decades, shifting attitudes have transformed how we view and use the plant due to the spread of legalization efforts. This has increased both access and potency, alongside scientific curiosity involving the plant’s effects on the human body, particularly on mental health.
Notably, various recent publications – a Canadian Medical Association Journal (CMAJ) summary on cannabis and psychosis, and a peer-reviewed Molecular Psychiatry study examining cannabis’ impact on DNA methylation in people with first-episode psychosis – have added depth to this discussion. Together, they highlight both the potential risks of heavy, high-potency cannabis use and the complex biology behind those risks.
THC Potency Increase and Mental Health Risks
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| THC Content | Typical Form | Relative Psychosis Risk |
|---|---|---|
| 4–8% | Low-potency flower | Baseline |
| 10–15% | Mid-potency flower | Slightly elevated |
| 20%+ | High-potency flower, concentrates | Significantly elevated, especially with frequent use |
According to the CMAJ report1, the THC content of cannabis has quintupled in just two decades. This means rising from about 4% in the early 2000s to over 20% in much of Canada’s legal dried flower by 2023. This is notable, as higher THC means more potent effects, good and bad. For example, risks include anxiety, paranoia, or, in rare cases, psychosis.
Psychosis, in particular, has garnered much attention. While the lifetime occurrence of cannabis-induced psychosis symptoms is relatively low, around 0.47% of users, the risk rises with certain factors:
- Using high-potency products (>10% THC)
- Frequent use
- Younger age
- Male sex
- Pre-existing mental health conditions such as depression or bipolar disorder
Thankfully, more than half of cannabis-related psychosis cases resolve within 24 hours. However, if symptoms last more than a week or there is a history of psychosis, hospitalization rates can be as high as 76%.
Links to Schizophrenia
Large-scale data from Ontario found that people who visited an emergency department for cannabis use had a 14-fold higher risk of developing a schizophrenia-spectrum disorder within three years. If that visit was specifically for cannabis-induced psychosis, the risk was over 240 times higher than in the general population.
What is important to recognize is that, while these statistics don’t mean cannabis causes schizophrenia in every case, they do highlight a strong association, particularly for those who may already be vulnerable.
Cannabis, DNA Methylation, and Psychosis Risk
Meanwhile, the Molecular Psychiatry study, which we have briefly looked at in the past, goes beyond population statistics and explores how cannabis might influence the body at a molecular level. In it, researchers analyzed blood samples from 682 people across two independent groups, including both cannabis users and non-users, some of whom had just experienced their first episode of psychosis.
They focused on DNA methylation – chemical tags that help regulate gene activity without altering the DNA sequence itself. The environment, lifestyle, and substances like cannabis can influence these epigenetic changes. Key findings included:
- Distinct molecular signatures of current cannabis use, even after adjusting for tobacco use.
- Changes in genes related to mitochondrial function — the cell’s “power plants” — including CAVIN1 and MCU. These genes are involved in energy production and may interact with cannabinoid receptors found in mitochondria.
- Pathway analysis suggests effects on immune system regulation, consistent with cannabis’s known immunomodulatory properties.
- In some cases, the impact of cannabis on DNA methylation was moderated by psychosis status, meaning that people with first-episode psychosis may show different biological responses to cannabis than those without.
Notably, the researchers found no evidence that cannabis use (even high-potency) accelerated biological aging, as measured by several “epigenetic clocks.”
Treatment and Recovery
For those who develop cannabis-induced psychosis, the mainstay of treatment is stopping cannabis use altogether, and continuing to use after a first episode is linked to higher relapse rates. Antipsychotic medications, particularly second-generation agents, can be prescribed for severe or persistent symptoms, to taper once stability is achieved.
Behavioral therapies such as motivational interviewing and cognitive behavioural therapy can help people reduce or quit cannabis use, manage cravings, and improve overall functioning.
Balancing Cannabis Benefits and Psychosis Risks
It’s important to remember that the majority of cannabis users will never experience psychosis. Many use cannabis for legitimate medical reasons, from chronic pain to seizure disorders, or simply for relaxation and social enjoyment. The risks are not evenly distributed; they’re shaped by genetics, mental health history, age of first use, frequency, and potency.
The takeaway from both studies is not a blanket warning to avoid cannabis entirely, but a call for informed, balanced use:
- Know your personal risk factors — if you have a family history of psychosis or severe mental illness, be extra cautious.
- Consider potency — products with very high THC levels may carry higher risks, especially without balancing CBD.
- Moderation matters — daily, high-potency use started at a young age carries the most significant risk.
- Stay informed — ongoing research is refining our understanding of cannabis’ effects at every level, from societal patterns to molecular pathways.
Together, these new insights reinforce an essential truth: cannabis, like alcohol or prescription medication, has both benefits and risks. Responsible use that is tailored to the individual’s biology and circumstances is key.
Studies Referenced:
1. Li, S., Solmi, M., Myran, D. T., & Fabiano, N. (2025). Cannabis and psychosis. CMAJ, 1https://doi.org/10.1503/cmaj.25065997(27), E810. https://doi.org/10.1503/cmaj.250659
2. Dempster, E. L., et al. (2025). Methylomic signature of current cannabis use in two first-episode psychosis cohorts. Molecular Psychiatry, 30, 1277–1286. https://doi.org/10.1038/s41380-024-02689-0
