Did Opening Cannabis Stores in California Increase Emergency Room Visits? | Research

The takeaway

Cities that authorized recreational cannabis stores saw increases in cannabis-related ER visits and poison center calls — and the effects spilled over into neighboring cities.

Local government officials deciding on cannabis retail policy, public health planners, health system administrators in legal cannabis states.

What the researchers found

Analyzing cannabis-related healthcare encounters across all 482 cities in California from 2010 to 2020, researchers found that authorizing storefront recreational cannabis retailers was associated with increases in three types of healthcare encounters.

Cities that permitted recreational dispensaries saw increases in population-adjusted emergency department visits, population-adjusted inpatient discharges, and the likelihood of poison center calls related to cannabis. The spatial difference-in-differences model — which accounts for both within-city changes over time and spatial relationships between cities — revealed something additional: the effects extended beyond the cities that authorized stores.

Neighboring cities that did not authorize their own retailers also experienced increases in cannabis-related healthcare encounters, suggesting a spatial spillover effect. People from cities without dispensaries appeared to be accessing cannabis from nearby authorized retailers and returning to their home communities, where any health complications would be treated locally.

Why it matters

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.

The numbers in context

482 California cities analyzed, 2010–2020 study period. Three outcomes measured: ED visits, inpatient discharges, and poison center calls. Both within-city and cross-city (spatial spillover) effects detected for cities authorizing recreational cannabis retailers.

How the study worked

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.

Who was studied

Data from 482 cities in California, USA from 2010 to 2020.

What this study cannot tell us

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.

How to read the evidence

Observational study with sophisticated spatial modeling — stronger than simple before/after comparisons but still cannot fully establish causation.

When this study was published

Published in 2026 using data through 2020. California's cannabis market has continued evolving since the study period.

The bigger picture

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.

Replication

Not stated in abstract.

Funding

Not reported in abstract.

Conflicts of interest

Not reported in abstract.

Questions still open

Do the healthcare increases stabilize or continue growing as cannabis markets mature? What types of cannabis-related emergencies are driving the ER visit increases — is it primarily edible overconsumption, pediatric exposures, or something else? Could mandatory product safety standards reduce healthcare encounters even as retail access expands?

Read the original research

Authorization of storefront recreational cannabis retailers and cannabis-related healthcare encounters: A local-level spatial difference-in-differences analysis in California, United States.

Addiction (Abingdon, England)

Addiction is a well-respected journal focusing on research related to substance use and addiction.

View on PubMed ↗Publisher’s paper ↗

Citation

Han, Bing; Gunadi, Christian; Shi, Yuyan. (2026). Authorization of storefront recreational cannabis retailers and cannabis-related healthcare encounters: A local-level spatial difference-in-differences analysis in California, United States.. Addiction (Abingdon, England). https://doi.org/10.1111/add.70318