Potency-Related Effects of Smoked Cannabis on Simulated Driving Performance: A Randomized, Controlled Crossover Trial

Authors

• Bruna Brands
• Adam Zaweel
• Madison Wright
• Patricia Di Ciano
• Christine M. Wickens
• Justin Matheson
• Andrew Fares
• Omer S. M. Hasan
• Marcos Sanches
• Beth Sproule
• Marilyn A. Huestis, Thomas Jefferson UniversityFollow
• Timothy L. Brown
• Bernard Le Foll

Document Type

Article

Publication Date

3-10-2026

Comments

This article is the author’s final published version in Scientific Reports, Volume 16, Issue 1, 2026, Article number 12961.

The published version is available at https://doi.org/10.1038/s41598-026-43045-2. Copyright © The Author(s) 2026.

Abstract

Given the increasing availability of high-potency Δ9-tetrahydrocannabinol (Δ9-THC) products, understanding potency-related effects of Δ9-THC on driving performance is an important public safety issue. This randomized, double-blind, placebo-controlled, within-subjects trial examined the effects of smoked cannabis with varying Δ9-THC concentrations on simulated driving. Adults aged 19–45 who regularly used cannabis and held valid driver’s licenses completed simulated driving tasks after smoking placebo, or cannabis containing low (6.25%/47 mg Δ9-THC), medium (12.5%/94 mg Δ9-THC), or high (22%/165 mg Δ9-THC) Δ9-THC levels. The primary outcome was mean speed (km/h); secondary measures included maximum speed, standard deviation of lateral position (SDLP), reaction time (RT), and subjective ratings of driving ability and intoxication. Mean speed did not differ across conditions. Maximum speed increased under medium (p = 0.006) and high (p = 0.02) potencies versus placebo. SDLP was higher across all Δ9-THC potencies (p < 0.001), and RT was longer under medium and high potencies (p < 0.001). Both SDLP (p < 0.001) and RT (p = 0.023) positively correlated with blood Δ9-THC concentrations. Participants reported poorer driving performance and reduced willingness to drive at higher potencies. Findings demonstrate potency-dependent impairments in simulated driving linked to Δ9-THC concentration, underscoring implications for road safety.

SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1038/s41598-026-43045-2.

Recommended Citation

Brands, Bruna; Zaweel, Adam; Wright, Madison; Di Ciano, Patricia; Wickens, Christine M.; Matheson, Justin; Fares, Andrew; Hasan, Omer S. M.; Sanches, Marcos; Sproule, Beth; Huestis, Marilyn A.; Brown, Timothy L.; and Le Foll, Bernard, "Potency-Related Effects of Smoked Cannabis on Simulated Driving Performance: A Randomized, Controlled Crossover Trial" (2026). Institute of Emerging Health Professions Faculty Papers. Paper 34.
https://jdc.jefferson.edu/iehpfp/34

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.

Language

English