Canada's cannabis legalization was not linked to increased traffic injuries in Ontario or Alberta
Analysis of over 239,000 traffic-injury emergency visits in Ontario and Alberta found no significant increase in driver injuries after cannabis was legalized in Canada in October 2018.
Quick Facts
What This Study Found
There was no evidence of significant changes in traffic-injury ED visits after cannabis legalization in either province, for all drivers or youth drivers specifically. Results were non-significant in all four analyses (Alberta all drivers p=0.52, Alberta youth p=0.42, Ontario all drivers p=0.30, Ontario youth p=0.98).
Key Numbers
Alberta: 52,752 all-driver presentations, 3,265 youth; Ontario: 186,921 all-driver, 4,565 youth; no significant changes post-legalization across all four analyses
How They Did This
SARIMA time series analysis of weekly provincial emergency department records from April 2015 to December 2019 in Alberta and Ontario, examining driver traffic-injury presentations before and after legalization (October 17, 2018).
Why This Research Matters
A primary concern about cannabis legalization was increased traffic injuries. This large population-level study from two major Canadian provinces provides reassuring evidence that this feared outcome did not materialize in the first year.
The Bigger Picture
This adds to evidence from U.S. states suggesting that cannabis legalization does not necessarily increase traffic injuries at the population level, though individual impaired driving remains a concern.
What This Study Doesn't Tell Us
Only 14 months of post-legalization data. ED visits may not capture all traffic injuries. Does not measure cannabis-impaired driving directly. Early legalization period may not reflect long-term trends.
Questions This Raises
- ?Would longer follow-up reveal delayed effects?
- ?Did cannabis-impaired driving increase but was offset by other safety improvements?
- ?Are there specific demographics or regions where traffic injuries did increase?
Trust & Context
- Key Stat:
- No significant change in traffic injuries after legalization in either province
- Evidence Grade:
- Large population-level time series analysis across two provinces with robust statistical methods
- Study Age:
- Published in 2021 covering through December 2019. Only 14 months of post-legalization data were available.
- Original Title:
- Canada's cannabis legalization and drivers' traffic-injury presentations to emergency departments in Ontario and Alberta, 2015-2019.
- Published In:
- Drug and alcohol dependence, 228, 109008 (2021)
- Authors:
- Callaghan, Russell C(2), Sanches, Marcos(8), Vander Heiden, Julia, Asbridge, Mark, Stockwell, Tim, Macdonald, Scott, Peterman, Bronwen Hughes, Kish, Stephen J
- Database ID:
- RTHC-03040
Evidence Hierarchy
Looks back at existing records to find patterns.
What do these levels mean? →Frequently Asked Questions
Did cannabis legalization increase traffic injuries in Canada?
This study found no evidence of increased driver traffic injuries in Ontario or Alberta in the first 14 months after legalization, for either all drivers or youth drivers.
Were youth drivers affected by legalization?
No. Despite concerns that legalization would particularly impact young drivers, there was no significant change in youth driver traffic-injury emergency visits in either province.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-03040APA
Callaghan, Russell C; Sanches, Marcos; Vander Heiden, Julia; Asbridge, Mark; Stockwell, Tim; Macdonald, Scott; Peterman, Bronwen Hughes; Kish, Stephen J. (2021). Canada's cannabis legalization and drivers' traffic-injury presentations to emergency departments in Ontario and Alberta, 2015-2019.. Drug and alcohol dependence, 228, 109008. https://doi.org/10.1016/j.drugalcdep.2021.109008
MLA
Callaghan, Russell C, et al. "Canada's cannabis legalization and drivers' traffic-injury presentations to emergency departments in Ontario and Alberta, 2015-2019.." Drug and alcohol dependence, 2021. https://doi.org/10.1016/j.drugalcdep.2021.109008
RethinkTHC
RethinkTHC Research Database. "Canada's cannabis legalization and drivers' traffic-injury p..." RTHC-03040. Retrieved from https://rethinkthc.com/research/callaghan-2021-canadas-cannabis-legalization-and
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.