What drugs were found in suspected impaired drivers in Quebec before cannabis legalization
Among nearly 3,000 suspected drug-impaired drivers evaluated in Quebec from 2014-2018, cannabis was detected in 48% of cases, while methamphetamine was the most common substance at 54%.
Quick Facts
What This Study Found
At least one impairing substance was detected in 98% of the 2,982 Drug Recognition Expert cases. Cannabis (THC-COOH) was found in 48% of cases. Polydrug use was common, with 79% of cases showing two or more impairing substances.
Key Numbers
Total cases: 2,982. Substance detected: 98%. Cannabis positive: 48%. Methamphetamine: 54%. Cocaine: 29%. GHB: 24%. Polydrug use: 79%. Average age: 33. Male: 79%.
How They Did This
Retrospective analysis of 2,982 Drug Recognition Expert evaluation cases in Quebec, Canada from January 2014 to December 2018. All biological samples underwent targeted LC-MS/MS analysis for 137 drugs and metabolites.
Why This Research Matters
Establishing a pre-legalization baseline of drug-impaired driving patterns helps researchers and policymakers measure the impact of recreational cannabis legalization on road safety.
The Bigger Picture
This pre-legalization snapshot provides a critical baseline for understanding how cannabis policy changes affect driving behavior and drug detection patterns.
What This Study Doesn't Tell Us
Only captures drivers flagged by police, not all impaired drivers. THC-COOH indicates past use rather than active impairment. Results reflect Quebec-specific drug culture and may not generalize.
Questions This Raises
- ?How have these detection patterns changed since cannabis legalization in October 2018?
- ?Does polydrug use complicate impairment assessment for DREs?
Trust & Context
- Key Stat:
- 48% of suspected impaired drivers tested positive for cannabis
- Evidence Grade:
- Comprehensive toxicological analysis with validated methods, though limited to drivers already flagged for impairment.
- Study Age:
- Published in 2021 covering 2014-2018, the period just before Canadian cannabis legalization.
- Original Title:
- Drugs and driving prior to cannabis legalization: A 5-year review from DECP (DRE) cases in the province of Quebec, Canada.
- Published In:
- Accident; analysis and prevention, 149, 105832 (2021)
- Authors:
- Vaillancourt, Lucie, Viel, Edith, Dombrowski, Cynthia, Desharnais, Brigitte, Mireault, Pascal
- Database ID:
- RTHC-03587
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
What was the most common drug found in suspected impaired drivers?
Methamphetamine was detected in 54% of cases, followed by cannabis at 48% and cocaine at 29%.
How common was polydrug use among suspected impaired drivers?
Very common. Two or more impairing substances were found in 79% of cases.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-03587APA
Vaillancourt, Lucie; Viel, Edith; Dombrowski, Cynthia; Desharnais, Brigitte; Mireault, Pascal. (2021). Drugs and driving prior to cannabis legalization: A 5-year review from DECP (DRE) cases in the province of Quebec, Canada.. Accident; analysis and prevention, 149, 105832. https://doi.org/10.1016/j.aap.2020.105832
MLA
Vaillancourt, Lucie, et al. "Drugs and driving prior to cannabis legalization: A 5-year review from DECP (DRE) cases in the province of Quebec, Canada.." Accident; analysis and prevention, 2021. https://doi.org/10.1016/j.aap.2020.105832
RethinkTHC
RethinkTHC Research Database. "Drugs and driving prior to cannabis legalization: A 5-year r..." RTHC-03587. Retrieved from https://rethinkthc.com/research/vaillancourt-2021-drugs-and-driving-prior
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.