A new study published in the Journal of the American Medical Association Network Open has found that cases of schizophrenia linked to cannabis use disorder have almost tripled over the past 17 years in Ontario, Canada. The research used data from healthcare visits of all Ontario residents aged 14 to 65 and found a significant increase in the proportion of new schizophrenia diagnoses associated with cannabis use disorder.
Before legalization, 4% of new cases were linked to cannabis use disorder. However, after cannabis was legalized in 2018, this number rose to 10%. The study also found that hospital care for cannabis use disorders increased by 270% between before and after legalization.
Researchers from ICES, the University of Ottawa, and Bruyère Health Research Institute analyzed data on emergency department visits, hospitalizations, and healthcare utilization. They estimated that if people with severe cannabis use had not stopped using cannabis during this period, up to 10% of new schizophrenia cases could have been prevented in men aged 14-24.
The study highlights the urgent need for targeted prevention strategies, particularly for younger populations who appear to be at greatest risk. Heavy cannabis use is associated with worsening symptoms and poorer prognosis for those living with schizophrenia. The authors emphasize that more research is needed to determine if heavy cannabis use can cause schizophrenia.
Source: https://medicalxpress.com/news/2025-02-cases-schizophrenia-linked-cannabis-disorder.html