Citation

Brubacher JR, Chan H, Erdelyi S, Macdonald S, Asbridge M, Mann RE, Eppler J, Lund A, Macpherson A, Martz W, Schreiber WE, Brant RF, Purssell RA. Addiction 2019; 114(9): 1616-1626.

Affiliation

The University of British Columbia, Vancouver, British Columbia.

Copyright

(Copyright © 2019, John Wiley and Sons)

DOI

10.1111/add.14663

PMID

31106494

Abstract

AIM: We conducted a responsibility analysis to determine whether drivers injured in motor vehicle collisions who test positive for Δ-9-tetrahydrocannabinol (THC) or other drugs are more likely to have contributed to the crash than those who test negative.

DESIGN: Prospective case-control study. SETTING: Trauma centres in British Columbia, Canada. PARTICIPANTS: Injured drivers who required blood tests for clinical purposes following a motor vehicle collision. MEASUREMENTS: Excess whole blood remaining after clinical use was obtained and broad spectrum toxicology testing performed. The analysis quantified alcohol and THCand gave semi-quantitative levels of other impairing drugs and medications. Police crash reports were analyzed to determine which drivers contributed to the crash (responsible) and which were "innocently involved" (non-responsible). We used unconditional logistic regression to determine the likelihood (Odds Ratio) of crash responsibility in drivers with 0
FINDINGS: We obtained toxicology results on 3005 injured drivers and police reports on 2318. Alcohol was detected in 14.4% of drivers, THC in 8.3%, other drugs in 8.9% and sedating medications in 19.8%. There was no increased risk of crash responsibility in drivers with THC<2ng/mL or 2≤THC<5ng/mL. In drivers with THC≥5ng/mL, the adjusted OR was 1.74 (95%CI=0.59-6.36;p=0.35). There was significantly increased risk of crash responsibility in drivers with BAC≥0.08% (OR=6.00;95%CI=3.87-9.75;p<0.01), other recreational drugs detected (OR=1.82;95%CI=1.21-2.80;p<0.01), or sedating medications detected (OR=1.45;95%CI=1.11-1.91;p<0.01).

CONCLUSIONS: In this sample of non-fatally injured motor vehicle drivers in British Columbia, Canada, there was no evidence of increased crash risk in drivers with THC<5ng/mL and a statistically non-significant increased risk of crash responsibility (OR=1.74) in drivers with THC≥5ng/mL.


Keyword: Cannabis impaired driving


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Language: en