Cannabis-Involved Traffic Injury ER Visits Rose 475% in Ontario Over a Decade, Accelerating After Commercialization

Annual rates of cannabis-involved traffic injury ER visits rose from 0.18 to 1.01 per 1,000 total motor vehicle collisions. Legalization with restrictions was associated with a 94% increase (aRR 1.94), while the commercialization/COVID period saw a 223% increase (aRR 3.23). Cannabis involvement remained rare overall (0.04% of traffic injury ER visits) compared to alcohol (0.8%). Males, ages 19-21, lowest-income neighborhoods, and prior cannabis-related ER visits were risk factors.

Repeated cross-sectional study of all traffic injury ER visits in Ontario, Canada (2010-2021) across three periods: pre-legalization, legalization with restrictions, and commercialization. Used quasi-Poisson models adjusting for season and time trends.

As jurisdictions legalize cannabis, tracking traffic safety outcomes is critical. This study suggests that the retail expansion phase, not initial legalization, may be when impaired driving increases most, though confounding with COVID-era changes in driving patterns complicates interpretation.

While the relative increase is dramatic, the absolute numbers are very small. Alcohol involvement in traffic injuries was 20 times more common than cannabis. The co-occurrence of commercialization with COVID-19, which changed driving patterns substantially, makes it hard to isolate the effect of expanded retail access.

Cannabis involvement was documented in only 0.04% of visits, so small absolute changes produce large relative changes. The commercialization period coincided with COVID-19, confounding the analysis. Relies on clinician documentation of cannabis involvement, which likely underestimates true prevalence.