Cannabis Legalization in Ontario Linked to Fewer ER Visits Among Schizophrenia Patients

Phase 1 legalization (flower/herbs) was associated with a 25.8% immediate decrease in cannabis-related ED visits among men with schizophrenia (95% CI 13.8-37.6%) and an 18.5% decrease in mental health-related ED visits among women (95% CI 6.0-31.2%). These decreases were specific to schizophrenia patients, not reflecting general population trends. Phase 2 (edibles/extracts) showed no significant changes.

Interrupted time-series analysis using linked Ontario health administrative data for 121,061 adults with schizophrenia from October 2015 to May 2021. Compared trends across pre-legalization, phase 1 (flowers/herbs), and phase 2 (edibles/extracts) with comparative ITS against general population.

People with schizophrenia were among the populations most feared to be harmed by legalization. This large-scale analysis from a universal healthcare system found the opposite: ER visits decreased after legalization, possibly because regulated products are safer than illicit ones.

The finding suggests that regulatory quality control (removing contaminants, standardizing potency) may reduce acute harms even in vulnerable populations. This challenges the assumption that any increase in cannabis access must harm people with psychotic disorders.

Observational design cannot prove legalization caused the decreases. COVID-19 overlapped with the study period and may have reduced ED visits generally. ICD-coded diagnoses may not perfectly capture CHS or cannabis-related presentations. Ontario-specific findings.