12.02.2025.
Recent research from Canada has strengthened the link between heavy cannabis use and an increased risk of developing schizophrenia and psychosis.
- The study analyzed medical records of over 13.5 million individuals aged 14 to 65 in Ontario between 2006 and 2022.
- Findings suggest that the proportion of new schizophrenia cases associated with cannabis use has nearly tripled over this period.
Rising cases of schizophrenia linked to Cannabis
The study revealed that before cannabis was legalized for recreational use in Canada in 2018, 3.7% of new schizophrenia cases were linked to cannabis use disorder.
After legalization, this figure rose to 10.3%. While the overall incidence of schizophrenia remained stable, cases of unspecified psychosis increased compared to pre-legalization levels.
Young men aged 19 to 24 showed the most significant increase. By the end of the study, nearly 19% of new schizophrenia cases in this group were associated with cannabis use disorder.
Previous research
Other studies have also indicated a connection between heavy cannabis use and schizophrenia. Research from Denmark published in 2021 found that schizophrenia cases linked to cannabis use disorder had increased three to fourfold over the past two decades.
A 2019 study conducted across 11 European sites found that daily cannabis use, particularly of high-potency strains, was strongly associated with the development of psychosis.
Implications for public health
The findings suggest that cannabis is not necessarily safe for all users, especially young people whose brains are still developing. The study adds to growing concerns that increased cannabis availability and higher potency products could contribute to a rise in psychiatric disorders.
As cannabis use continues to grow globally, these results highlight the need for greater awareness of potential mental health risks, especially among younger users.
Limitations
The study did not account for factors such as income, education, genetic predisposition, or family history of mental illness, which could influence results. It also only included individuals who required emergency or hospital care for cannabis use disorder, meaning the true impact may be higher.
Additionally, the COVID-19 pandemic may have affected data collection. Future research is needed to assess the long-term effects of increasing THC levels in cannabis products.
