Cannabis was the most common drug found in suspected impaired drivers in Ontario
Cannabis was detected in 52.8% of suspected drug-impaired drivers in Ontario from 2008-2019, followed by cocaine (44.3%) and methamphetamine (24.8%), with 80% of cases involving multiple substances.
Quick Facts
What This Study Found
Over 12 years, 5,388 samples from suspected drug-impaired drivers were analyzed. Cannabis was most frequently detected (52.8%), followed by cocaine (44.3%) and methamphetamine (24.8%). Eighty percent of cases involved more than one substance. Sample submissions increased after cannabis legalization in 2018.
Key Numbers
5,388 samples over 12 years. Cannabis: 52.8%. Cocaine: 44.3%. Methamphetamine: 24.8%. Multiple substances: 80%. Samples increased after Drug Evaluation and Classification Program implementation and cannabis legalization.
How They Did This
Retrospective analysis of blood and urine samples submitted to Ontario's Centre of Forensic Sciences from suspected drug-impaired drivers (2008-2019). Standardized comprehensive toxicological analysis tested for a wide variety of impairing drugs.
Why This Research Matters
Understanding which substances impaired drivers use, and how often they combine them, helps shape enforcement strategies and public safety messaging. Cannabis as the top substance has implications for post-legalization road safety.
The Bigger Picture
The 80% polysubstance rate means cannabis-impaired driving rarely occurs in isolation, complicating efforts to attribute impairment to any single substance and highlighting the challenge of setting cannabis-specific driving limits.
What This Study Doesn't Tell Us
Only suspected impaired drivers (not a random sample). Detection does not equal impairment (cannabis can be detected days after use). Sample collection increased over time due to more trained officers, not necessarily more impaired driving. Ontario-specific data.
Questions This Raises
- ?Did cannabis legalization actually increase impaired driving, or just detection?
- ?How should enforcement handle the 80% polysubstance rate when attributing impairment?
- ?Are current THC per se limits appropriate given detection windows?
Trust & Context
- Key Stat:
- 52.8% of impaired drivers tested positive for cannabis
- Evidence Grade:
- Large forensic toxicology dataset provides comprehensive detection data, but samples are from suspected drivers (selection bias) and detection does not equal impairment.
- Study Age:
- 2024 analysis of Ontario forensic toxicology data from 2008-2019
- Original Title:
- Toxicology findings from drivers suspected of drug-impaired driving in Ontario (2008-2019).
- Published In:
- Traffic injury prevention, 25(7), 894-901 (2024)
- Authors:
- Beirness, Douglas J(4), Rajotte, James W, Peaire, Amy E
- Database ID:
- RTHC-05128
Evidence Hierarchy
Frequently Asked Questions
Is cannabis the most common drug in impaired drivers?
In Ontario, yes. Cannabis was detected in 52.8% of suspected drug-impaired drivers, more than cocaine (44.3%) or methamphetamine (24.8%).
Does finding cannabis mean the driver was impaired by cannabis?
Not necessarily. Cannabis can remain detectable in blood for hours to days after the impairing effects have worn off. Additionally, 80% of cases involved multiple substances, making it difficult to attribute impairment to cannabis alone.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-05128APA
Beirness, Douglas J; Rajotte, James W; Peaire, Amy E. (2024). Toxicology findings from drivers suspected of drug-impaired driving in Ontario (2008-2019).. Traffic injury prevention, 25(7), 894-901. https://doi.org/10.1080/15389588.2024.2355593
MLA
Beirness, Douglas J, et al. "Toxicology findings from drivers suspected of drug-impaired driving in Ontario (2008-2019).." Traffic injury prevention, 2024. https://doi.org/10.1080/15389588.2024.2355593
RethinkTHC
RethinkTHC Research Database. "Toxicology findings from drivers suspected of drug-impaired ..." RTHC-05128. Retrieved from https://rethinkthc.com/research/beirness-2024-toxicology-findings-from-drivers
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.