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The effect of alcohol, THC and their combination on perceived effects, willingness to drive and performance of driving and non-driving tasks.

Adi Ronen, Hadas Schwartz Chassidim, Pnina Gershon, Yisrael Parmet, Alex Rabinovich, Rachel Bar-Hamburger, Yair Cassuto, David Shinar

Accident; Analysis and Prevention November 2010 DOI: 10.1016/j.aap.2010.05.006 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Within-subjects experimental study Peer reviewed
Sample size 12
Population Healthy recreational users of alcohol and marijuana, ages 24-29
Interventions Alcohol THC
Dose BAC=0.05%, THC 13 mg
Topics Cannabis
Key findings Alcohol combined with THC produced the most intense effects, impairing driving and non-driving task performance, increasing subjective sensations, and altering heart rate. Despite significant differences in effect size across treatments, participants reported willingness to drive similar distances under all conditions, indicating their driving intentions did not reflect their actual level of impairment.

Abstract

Driving under the influence of drugs (DUID) is one of the main causes of car accidents. Alcohol and marijuana are the most popular drugs among recreational users. Many classify these drugs as "Light" drugs and therefore allow themselves to drive after consuming them. The study had two main objectives: 1) to investigate the effect of alcohol (BAC=0.05%), THC (13 mg) and their combination on driving and non-driving tasks. 2) to investigate the extent to which people are willing to drive based on their subjective sensations and their perceived effects of the drugs. 7 healthy men and 5 healthy women, ages 24-29, all recreational users of alcohol and marijuana, completed 5 experimental sessions. Sessions included: drinking and smoking placebo, drinking alcohol and smoking placebo, drinking placebo and smoking THC, drinking alcohol and smoking THC, drinking placebo and smoking placebo 24 hours after drinking alcohol and smoking THC. Three types of measures were used: subjective perceptions (with questionnaires), performance parameters of the driving and non-driving tasks (arithmetic task and a secondary target detection task) and physiological changes (heart rate). Overall, the combination of alcohol and THC had the most intense effect after intake. This effect was reflected in performance impairments observed in the driving and non-driving tasks, in the subjective sensations after intake, and in the physiological measures. Despite significant differences in the size of the effects after the various treatments, there were no differences in the distances subjects were willing to drive while under the influence on each of the treatments.

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