Did Opening Cannabis Stores in California Increase Emergency Room Visits?

Secondary data analysis using a spatial difference-in-differences model at the city-quarter level across 482 California cities from 2010 to 2020. Three outcome measures: population-adjusted ED visits, population-adjusted inpatient discharges, and any poison center calls. Controlled for time-varying city-level policies and sociodemographic factors while accounting for spatial influence across neighboring cities.

This is one of the most methodologically sophisticated studies of how cannabis retail access affects healthcare utilization. The spatial spillover finding is particularly important for local policy debates: cities that opt out of allowing dispensaries may not be fully insulated from the health effects if neighboring cities opt in.

This study addresses the local dimension of cannabis legalization that state-level analyses miss. While state legalization sets the framework, individual cities decide whether to allow retail stores — and this research shows that those local decisions have measurable health system consequences that extend beyond city boundaries. It connects to the broader legalization outcome literature (RTHC-00253 on college student use, RTHC-00229 on pregnancy treatment completion) by showing that retail access is a distinct policy variable with its own effects.

Observational study — cannot establish that dispensary authorization caused the increases (other policy or demographic changes may have occurred simultaneously). Cannabis-related healthcare encounters likely undercount actual health events. The 2010–2020 timeframe captures early legalization effects; patterns may have changed as the market matured. California's local option system may not generalize to states with different regulatory approaches.