Visual function and vehicle driving performance under the effects of cannabidiol: A randomized cross-over experiment

Abstract

Aims: This study aimed to determine the effect of vaporized cannabidiol (CBD) on visual function and vehicle driving performance, given the growing popularity of CBD use worldwide. Design: Randomized, double-blind, placebo-controlled cross-over experimental study. Setting: Laboratory of Vision Sciences and Applications, University of Granada, Spain. Participants: Thirty participants were recruited through advertisements placed in the local newspaper and distributed among the university community. They had a mean age of 26.2 (6.2) years, and 70% were male. All of them were occasional users of CBD or cannabis, and held valid driving licenses. Interventions: Three experimental sessions, conducted one week apart, in which a placebo, 15% CBD (16 mg) or 30% CBD (32 mg) was vaporized. Measurements: The primary endpoint for driving performance was the overall driving performance score (ODPS). Secondary outcomes included visual function variables such as static and dynamic visual acuity, stereoacuity, contrast sensitivity, motion detection and other driving performance parameters such as mean speed, lateral vehicle control or reaction time. Findings: Comparisons revealed no statistically significant changes in ODPS after vaporizing CBD at 15% or 30% compared with the placebo (χ2 = 0.479; P = 0.787). Visual function remained largely unchanged, with only a statistically significant decrease in motion detection (χ2 = 7.980; P = 0.018). Similarly, no statistically significant differences were found in driving performance secondary outcomes, such as the standard deviation of lateral lane position (χ2 = 0.068; P = 0.966), distance travelled outside the lane (χ2 = 2.530; P = 0.282), reaction time (χ2 = 1.000; P = 0.607), or collisions (χ2 = 0.987; P = 0.610). Additionally, correlations between ODPS and visual function did not yield statistically significant results. Conclusions: Consumption of vaporized cannabidiol in 16 mg and 32 mg doses does not appear to affect simulated vehicle driving performance and visual function.