PubMed: High 'N' Dry? A Comparison of Cannabis and Alcohol Use in Drivers Presenting to Hospital after a Vehicular Collision

Addiction. 2023 Mar 10. doi: 10.1111/add.16186. Online ahead of print.

ABSTRACT

BACKGROUND AND AIMS: The characteristics of cannabis-involved motor vehicle collisions are poorly understood. This study of injured drivers identifies demographic and collision characteristics associated with high tetrahydrocannabinol (THC) concentrations.

DESIGN: Prospective observational study.

SETTING: Fifteen Canadian trauma centres between January 2018 and December 2021. Cases Injured drivers (n=6956) who required blood testing as part of routine trauma care.

MEASUREMENTS: We quantified whole blood THC and blood alcohol concentration (BAC) and recorded driver sex, age and postal code, time of crash, crash type and injury severity. We defined three driver groups: High THC (THC≥5ng/mL & BAC=0); High Alcohol (BAC≥0.08% & THC=0) and THC/BAC negative (THC = 0 = BAC). We used logistic regression techniques to identify factors associated with group membership.

FINDINGS: Most injured drivers (70.2%) were THC/BAC negative; 1,274 (18.3%) had THC>0 including 186 (2.7%) in the High THC group; 1161 (16.7%) had BAC>0 including 606 (8.7%) in the high BAC group. Males and drivers <45 years had higher adjusted odds of being in the High THC group (v.s., THC/BAC negative group). Importantly, 4.6% of drivers <19 years old had THC≥5ng/mL and drivers <19 years had higher unadjusted odds of being in the High THC group than drivers aged 45-54 years old. Males, drivers aged 19-44 years, rural drivers, seriously injured drivers, and drivers injured in single-vehicle, nighttime or weekend collisions had higher adjusted odds ratios [aORs] for being in the High Alcohol group (v.s., THC/BAC negative). Drivers aged <35 or ≥ 65 years and drivers involved in multi-vehicle, daytime or weekday collisions had higher adjusted odds for being in the High THC group (v.s., High BAC group).

CONCLUSIONS: In Canada, risk factors for cannabis-related motor vehicle collisions appear to differ from those for alcohol-related motor vehicle collisions. The collision factors associated with alcohol (single vehicle, nighttime, weekend, rural, serious injury) are not associated with cannabis-related collisions. Demographic factors (young drivers, male drivers) are associated with both alcohol and cannabis-related collisions but are more strongly associated with cannabis-related collisions.

FUNDING: This study received funding from Health Canada, CIHR, Ministries of Transportation of Alberta and Ontario and Saskatchewan Government Insurance.

PMID:36898848 | DOI:10.1111/add.16186