Cannabis Effects on Driving Skills

Abstract

BACKGROUND Cannabis is the most prevalent illicit drug identified in impaired drivers. The effects of cannabis on driving continue to be debated, making prosecution and legislation difficult. Historically, delays in sample collection, evaluating the inactive Δ9-tetrahydrocannabinol (THC) metabolite 11-nor-9-carboxy-THC, and polydrug use have complicated epidemiologic evaluations of driver impairment after cannabis use. CONTENT We review and evaluate the current literature on cannabis’ effects on driving, highlighting the epidemiologic and experimental data. Epidemiologic data show that the risk of involvement in a motor vehicle accident (MVA) increases approximately 2-fold after cannabis smoking. The adjusted risk of driver culpability also increases substantially, particularly with increased blood THC concentrations. Studies that have used urine as the biological matrix have not shown an association between cannabis and crash risk. Experimental data show that drivers attempt to compensate by driving more slowly after smoking cannabis, but control deteriorates with increasing task complexity. Cannabis smoking increases lane weaving and impaired cognitive function. Critical-tracking tests, reaction times, divided-attention tasks, and lane-position variability all show cannabis-induced impairment. Despite purported tolerance in frequent smokers, complex tasks still show impairment. Combining cannabis with alcohol enhances impairment, especially lane weaving. SUMMARY Differences in study designs frequently account for inconsistencies in results between studies. Participant-selection bias and confounding factors attenuate ostensible cannabis effects, but the association with MVA often retains significance. Evidence suggests recent smoking and/or blood THC concentrations 2–5 ng/mL are associated with substantial driving impairment, particularly in occasional smokers. Future cannabis-and-driving research should emphasize challenging tasks, such as divided attention, and include occasional and chronic daily cannabis smokers.

Controlled Cannabis Vaporizer Administration: Blood and Plasma Cannabinoids with and without Alcohol

“…2), similar to the window of acute intoxication (40 ). A higher 5-g/L cutoff results in a short detection window for occasional to moderate smokers-shorter than impairment windows (5,40 )-emphasizing the challenge in establishing appropriate science-based per se cannabis drugged driving legislation. Role of Sponsor: NHTSA played a direct role in the design of the study and review and interpretation of data.…”

Development of a rapid column-switching LC-MS/MS method for the quantification of THCCOOH and THCCOOH-glucuronide in whole blood for assessing cannabis consumption frequency

“…Not surprisingly, roadside surveys have demonstrated that driving under the influence of cannabis (DUIC) is a common and widespread occurrence [2][3][4][5]. Cannabis consumption has been shown to have impairing effects on cognitive functions and psychomotor skills related to driving and to be associated with an elevated accident risk [6][7][8][9]. Thus, DUIC has severe implications on global road safety and is considered a serious criminal offense in many countries [10].…”

Under the influence: examination of prevalence and correlates of alcohol and marijuana consumption in relation to youth driving and passenger behaviours in Canada. A cross-sectional study

“…16 Debate exists regarding the extent to which driving under the influence of cannabis causes motor vehicle fatalities. [17][18][19][20][21] In Ontario in 2015, 12% of grade 7-12 students rode with a driver who had used drugs, including cannabis, at least once in the previous year. 22 In light of the impending legalization of cannabis in Canada, we aimed to determine what individual and area-level characteristics are associated with risky driving and passenger behaviours among grade 9-12 students in Canada.…”