THC was found in more fatally injured Ontario drivers than alcohol between 2016 and 2018
In a study of 921 driver fatalities in Ontario, more tested positive for THC (251) than for alcohol (241), with 38% of positive cases involving multiple substances.
Quick Facts
What This Study Found
Among 921 driver fatalities, 53.7% tested positive for at least one substance. THC positivity (251 cases) exceeded alcohol (241 cases). Alcohol-related fatalities clustered on weekends in single-vehicle crashes, while THC-positive fatalities were spread throughout the week and more often involved multi-vehicle crashes.
Key Numbers
921 driver fatalities; 53.7% tested positive for a substance; 251 THC-positive; 241 alcohol-positive; 235 positive for other drugs; 38% of positive cases had multiple substances
How They Did This
Toxicological analysis of postmortem blood samples from 921 drivers who died in crashes in Ontario, Canada from January 2016 through December 2018, with demographic and crash characteristics coded into a database.
Why This Research Matters
The finding that THC now appears in more fatally injured drivers than alcohol signals a shift in impaired driving patterns that requires new prevention strategies beyond traditional alcohol-focused approaches.
The Bigger Picture
As cannabis legalization expands in Canada and elsewhere, this data provides a baseline for monitoring how changing cannabis laws affect road safety and whether new intervention strategies are needed.
What This Study Doesn't Tell Us
Postmortem THC detection does not prove impairment at time of crash. Single province data may not generalize nationally. No comparison with non-fatal crashes or general driving population.
Questions This Raises
- ?Has the pattern changed since cannabis legalization in Canada (October 2018)?
- ?What THC concentrations were found, and do they correlate with crash type?
- ?Would roadside impairment testing have prevented these crashes?
Trust & Context
- Key Stat:
- 251 driver fatalities tested positive for THC vs 241 for alcohol
- Evidence Grade:
- Large toxicological study of real-world driver fatalities with comprehensive testing
- Study Age:
- Published in 2021 using 2016-2018 data from Ontario. Cannabis was legalized in Canada in October 2018, so this data spans both pre- and post-legalization periods.
- Original Title:
- Cannabis, alcohol and other drug findings in fatally injured drivers in Ontario.
- Published In:
- Traffic injury prevention, 22(1), 1-6 (2021)
- Authors:
- Beirness, Douglas J(4), Gu, Kai Wen, Lowe, Nicholas J, Woodall, Karen L, Desrosiers, Nathalie A, Cahill, Brent, Porath, Amy J, Peaire, Amy
- Database ID:
- RTHC-02996
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Is THC now more common than alcohol in driver fatalities?
In this Ontario study, yes. THC was detected in 251 driver fatalities compared to 241 for alcohol between 2016 and 2018. However, detection does not prove impairment at the time of the crash.
Do cannabis-impaired crashes look different from alcohol-impaired crashes?
This study found alcohol-related fatalities clustered on weekends and were more often single-vehicle crashes, while THC-positive fatalities were spread throughout the week and more often involved multi-vehicle collisions.
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Cite This Study
https://rethinkthc.com/research/RTHC-02996APA
Beirness, Douglas J; Gu, Kai Wen; Lowe, Nicholas J; Woodall, Karen L; Desrosiers, Nathalie A; Cahill, Brent; Porath, Amy J; Peaire, Amy. (2021). Cannabis, alcohol and other drug findings in fatally injured drivers in Ontario.. Traffic injury prevention, 22(1), 1-6. https://doi.org/10.1080/15389588.2020.1847281
MLA
Beirness, Douglas J, et al. "Cannabis, alcohol and other drug findings in fatally injured drivers in Ontario.." Traffic injury prevention, 2021. https://doi.org/10.1080/15389588.2020.1847281
RethinkTHC
RethinkTHC Research Database. "Cannabis, alcohol and other drug findings in fatally injured..." RTHC-02996. Retrieved from https://rethinkthc.com/research/beirness-2021-cannabis-alcohol-and-other
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.