Emergency department use by individuals with and without psychosis after state-level cannabis legalization and commercialization.

Hyatt A.; Flores M.; Overhage L.; Bien-Aime D.; Evins A.; Öngür D.; Lê Cook B. · Nature. Mental health · 2026

**Background & Methods** This longitudinal cohort study utilized nationally representative survey data (2013-2022) to examine emergency department (ED) utilization trends following recreational cannabis legalization and retail outlet opening in US states. The researchers employed difference-in-difference (DiD) statistical methods to compare ED visit patterns among individuals with psychotic disorders versus the general population without psychosis over 3 years of follow-up. **Key Findings** - Cannabis retail outlet opening was associated with a statistically significant increase in ED visits among individuals with psychosis in legalization states (0.43 additional visits per person per year; 95% CI -0.014 to 0.85; P = 0.043), representing approximately 51% more annual ED utilization. - No significant increase in ED visits was observed in the general population without psychosis following retail outlet opening (DiD estimate -0.015; 95% CI -0.03 to 0.06; P = 0.54). - Exploratory subgroup analyses revealed that the increased ED utilization among individuals with psychosis was specifically driven by those with past-year cannabis use, suggesting active cannabis consumers with psychotic disorders represent the highest-risk population. **Dosage & Administration** Not reported. **Safety & Adverse Effects** The study did not specify particular adverse events or symptom presentations driving ED visits. However, the findings suggest cannabis use among individuals with psychosis is associated with worsening health outcomes requiring emergency care, indicating potential exacerbation of psychotic symptoms or related complications. **Evidence Quality** Strengths include the nationally representative sample, 9-year data collection period, and robust DiD methodology controlling for state-level and temporal confounders. Limitations include reliance on survey data rather than clinical diagnoses, inability to determine specific reasons for ED visits, potential unmeasured confounding variables, and borderline statistical significance with confidence intervals approaching zero. The study provides observational evidence only and cannot establish causality. Generalizability may be limited by regional variation in legalization timing and cannabis product characteristics. The findings represent early evidence requiring replication with larger clinical samples and prospective designs to establish definitive causal relationships between cannabis commercialization and psychosis-related morbidity.

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