Neighborhood exposure to cannabis stores increases cannabis-related emergency department visits

1. In this quasi-experimental study, Ontario neighbourhoods with cannabis stores experienced relatively  higher rates of cannabis-related emergency department (ED) visits.

2. Neighborhoods with more cannabis stores experienced greater increases in cannabis-related ED visits.

Evidence Rating Level: 2 (Good)

Study Rundown: While higher densities of alcohol and tobacco outlets are linked to greater health harms, evidence regarding cannabis stores is limited. This study investigated whether neighborhood exposure to cannabis stores following Canada’s 2018 legalization of non-medical cannabis influenced rates of cannabis-attributable emergency department (ED) visits in Ontario. Prior to legalization, cannabis-related ED visits had been increasing. Analyzing nearly 20,000 neighborhoods, researchers found that neighborhoods exposed to a cannabis store did not see monthly increases in cannabis-related ED visits, whereas unexposed neighborhoods experienced declines, yielding a 12% relative increase in exposed versus unexposed neighborhoods. Increases were more pronounced in males. Among individuals aged 15-24 years, visit rates remained stable in exposed neighborhoods but decreased in unexposed ones; among those aged 25-64 years, rates rose in exposed neighborhoods and either decreased or remained stable in unexposed neighborhoods. Secondary analyses found no effect of greater distances to stores on visit rates, but neighborhoods with more stores experienced higher rates of ED visits. Limitations include potential unmeasured confounding variables, COVID-19 impacts, and possible reporting or diagnostic biases. Overall, the findings suggest that neighborhood exposure to cannabis stores is associated with higher rates of cannabis-attributable ED visits, indicating that commercialization may contribute additional harms beyond legalization alone.

Click to read this study in AIM

Relevant Reading: Public health implications of legalising the production and sale of cannabis for medicinal and recreational use

In-Depth [prospective cohort]: This study evaluated whether neighborhood exposure to cannabis stores was associated with changes in monthly emergency department (ED) visit rates. All Ontario residents aged 15-105 eligible for the Ontario Health Insurance Plan (OHIP) were assigned to 20,048 neighborhoods based on postal code, excluding those not OHIP-eligible for at least 2 years prior. All cannabis retail stores in Ontario were geolocated, and store distances of 1,000, 2,000, and 3,000 m along the road network from neighborhood centers were calculated monthly. Neighborhoods were defined as exposed if a store was within 1,000 m. The study period spanned April 2017 to December 2022. The primary outcome was the neighborhood-level rate of cannabis-attributable ED visits per 100,000 individuals aged ≥15. The analysis included 19,098 neighborhoods with 11,137,625 individuals. By study end, 5,812 neighborhoods (30.4%) containing 3,263,956 individuals (29.3%) had a cannabis store within 1,000 m. Exposed and unexposed neighborhoods were similar in sex, age, immigration status, and prevalence of substance use or psychiatric diagnoses but differed in urbanicity and income: exposed neighborhoods were more likely urban (SMD, 0.28 vs. 0.27 rural) and in the lowest income quintile (SMD, 0.50 vs. 0.35 highest quintile). Exposed neighborhoods had a median of 1.0 store (IQR, 1-2). The primary matched analysis included 6,140,595 individuals in 10,574 neighborhoods, with 33,550 cannabis-attributable ED visits, most commonly for harmful use (49.7%) and acute intoxication (17.3%). Monthly visit rates were stable in exposed neighborhoods (absolute rate difference [RD], 0.24 [95% CI, -0.29 to 0.77] per 100,000 persons) but decreased in unexposed neighborhoods (RD, -1.06 [CI, -1.64 to -0.48] per 100,000 persons), yielding a 12% relative increase in exposed neighborhoods. Increases in ED visits were larger in males (RD difference, 1.35 [CI, 0.13-2.56]; p = 0.03) than females (RD difference, 1.08 [CI, 0.14-2.02]; p = 0.25). For residents aged 15-24, cannabis-related ED visit rates stayed steady in neighborhoods with stores but declined in neighborhoods without them. Among those aged 25-64, visit rates rose in exposed neighborhoods while remaining stable or falling in unexposed neighborhoods. The gap between exposed and unexposed neighborhoods was greatest in younger age groups. Additional analyses showed that distance to stores did not significantly affect visit rates, but neighborhoods with more stores experienced larger increases. Overall, neighborhood exposure to cannabis stores appears associated with increased rates of cannabis-attributable ED visits, suggesting commercialization may add harms beyond legalization alone.

Image: PD

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