Acute Inhaled Cannabis and Oral Alcohol: Simulated Driving Performance and Subjective Driving Confidence in Humans

Authors

Maribeth Stafford 1, Paul A. Nuzzo 1,3, Michelle Lofwall 1-4, Laura Fanucchi 3,4, Sharon Walsh 1-3,5,6, Shanna Babalonis 1-3; 1 University of Kentucky, College of Medicine, 2 Department of Behavioral Science, 3 Center on Drug and Alcohol Research, 4 Department of Psychiatry, 5 Department of Internal Medicine, 6 Department of Pharmacology and Nutritional Science

Introduction

As cannabis becomes more widely available, determining its effects on driving performance is imperative to public health. The aim of the current study was to compare a range of inhaled cannabis doses (relevant to current medical/recreational products) to the effects of an intoxicating dose of oral alcohol (0.08 breath alcohol concentration).

Methods

Healthy cannabis users were enrolled in this within-subject, randomized, double-blind, double-dummy, placebo-controlled, outpatient study (n=9), where driving performance was assessed in a driving simulator. Across 5 experimental sessions the effects of inhaled cannabis (0, 15, 30 mg THC; 15 mg THC+7.5 mg CBD) and oral alcohol (0, 0.8g/kg [15% less for women]) were assessed. Data were collected at baseline and for 6 hrs after drug administration. Primary outcomes included standard deviation of lane position (SDLP), variability of speed and steering, and reaction time. Secondary outcomes included subjective ratings of driving performance and abuse potential outcomes.

Results

Alcohol produced robust impairments in simulated driving performance (e.g., increased Standard Deviation of Lane Position (SDLP) and speed; p<.05), while cannabis negatively impacted a different array of driving outcomes (e.g., decreased brake force, headway distance during obstacle navigation; p<.05). All active doses of alcohol and cannabis decreased driving confidence (e.g., willingness to operate a real vehicle; p<.05) and increased ratings on abuse potential outcomes (p<.05). Both active alcohol and 30mg THC increased ratings of subjective impairment (p<.05).

Conclusion

Cannabis did not produce profound alcohol-like impairment; however, it was not without risk. Cannabis impaired select driving outcomes (e.g., decreased brake force, decreased maneuvering in response to obstacle). All active cannabis doses decreased participants' willingness to drive and high dose THC increased self-reported impairment. Overall, even in a sample of regular cannabis users, cannabis decreased driving acuity and confidence in safe driving ability.

References

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