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

The takeaway

After Canada legalized cannabis, patients with schizophrenia in Ontario saw significant decreases in cannabis-related, mental health-related, and psychosis-related ER visits, contradicting fears that legalization would worsen outcomes for this population.

Psychiatrists, legalization policymakers, mental health advocates, patients with psychotic disorders

25.8% drop in cannabis-related ER visits after legalization

What the researchers found

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.

Why it matters

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 numbers in context

121,061 schizophrenia patients; 25.8% decrease in cannabis ED visits (men); 18.5% decrease in mental health ED visits (women); changes distinct from general population trends.

How the study worked

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.

What this study cannot tell us

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.

How to read the evidence

Large population-based interrupted time-series with comparative analysis, though limited by observational design and COVID overlap.

When this study was published

2025 publication with data 2015-2021

The bigger picture

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.

Questions still open

Is the reduction driven by safer regulated products or by changes in help-seeking behavior?
Why did phase 2 (edibles/extracts) show no additional effect?

Common questions

Does cannabis legalization make things worse for people with schizophrenia?

This Ontario study of 121,061 schizophrenia patients found the opposite: cannabis-related and mental health-related ER visits decreased after legalization. The authors suggest regulated products may be safer than illicit ones.

Did edible legalization affect schizophrenia patients differently?

No. While the initial legalization of cannabis flowers was associated with decreased ER visits, the second phase legalizing edibles, extracts, and topicals showed no additional significant changes.

Read the original research

The impact of recreational cannabis legalization on cannabis-related acute care events among adults with schizophrenia.

Social psychiatry and psychiatric epidemiology, 60(6), 1391-1398

View on PubMed ↗Publisher’s paper ↗

Citation

Kim, Chungah; Bai, Yihong; Cao, Peiya; Ienciu, Kristine; Chum, Antony. (2025). The impact of recreational cannabis legalization on cannabis-related acute care events among adults with schizophrenia.. Social psychiatry and psychiatric epidemiology, 60(6), 1391-1398. https://doi.org/10.1007/s00127-024-02773-4