Study examines cannabidiol's effect on simulated driving

By Dr. Chinta SidharthanNov 29 2022Reviewed by Benedette Cuffari, M.Sc.

In a recent study published in AJPM Focus, researchers discuss the results of a randomized pilot clinical trial using simulated driving performance to investigate whether drowsiness induced by the medical use of cannabidiol had an impact on safe driving.

Study: The effects of cannabidiol on the driving performance of healthy adults: a pilot randomized clinical trial. Image Credit: hallojulie / Shutterstock.com

Background

With growing evidence of the therapeutic properties of cannabidiol, the United States Food and Drug Administration (FDA) has approved cannabidiol oil (Epidiolex) to treat Dravet syndrome, Tuberous Sclerosis Complex, and Lennox‐Gastaut syndrome in children. Non-prescription cannabidiol-containing products, which contain lower concentrations of cannabidiol than prescriptions, have been available since 2018.

One of the known side effects of cannabidiol is drowsiness. While various placebo-controlled clinical trials have investigated the effectiveness of cannabidiol in clinical populations with neuropsychiatric and neurological problems, limited studies have explored the effects of non-prescription cannabidiol on activities such as driving.

About the study

In the present study, researchers compare the simulated driving performance in adults randomly administered non-prescription cannabidiol or placebo. The clinical trial was a double-blind, parallel-group, pilot feasibility study for maximum patient retention.

Individuals were eligible to participate in the study if they were between the ages of 18 and 30, had a valid driver’s license, were enrolled as a student, had driven more than once in the past month, were not on any other prescription medications, not including birth control, had no serious chronic diseases, agreed to a urine drug test and a test drive to rule out simulation sickness, and made arrangements for a ride home after testing. Individuals were excluded from the study if they had used cannabidiol in the past week, generally used tobacco or illegal drugs, or were pregnant or lactating.

All participants were required to complete a demographic survey and various cognitive and psychomotor tests. They were then randomly allocated to the cannabidiol treatment or placebo group.

The placebo consisted of avocado oil. Both the treatment and placebo were identically flavored. After administration of the treatment or placebo, all participants performed a driving simulation according to instructions.

Driving performance was measured using five primary and three secondary outcomes. The standard deviation of lateral position was the first primary outcome.

Time spent driving beyond the shoulder or centerline of the roadway was the second primary outcome. The total number of collisions, time to the first collision, and mean brake reaction time were the third, fourth, and fifth primary outcomes, respectively.

Secondary outcomes included the total time taken by the participant to complete the drive, time spent driving over the designated speed limit, and usage of turn signals.

Study findings

The primary and secondary outcomes of the simulated driving performance did not differ significantly between the treatment and placebo groups. However, the participants in the treatment group showed a 35% higher likelihood of colliding than those in the placebo group. Furthermore, participants who were administered cannabidiol drove slower than those who received the placebo.

The authors believe that though not significant, the study findings indicate the need for caution. Participants in the treatment group performed slightly worse along all primary and secondary outcomes as compared to those in the placebo group. Drivers who are impaired generally have slower reaction times, as well as difficulty maintaining speed and staying within lanes.

The non-prescription usage of cannabidiol presents other concerns. Cannabidiol is often incorporated into various consumable products and is mislabeled, with the product containing more Δ9-tetrahydrocannabinol (THC) than is legally allowed, which can impair safe driving abilities.

Some of the limitations of the current study include the fact that only one dose of cannabidiol was administered to the participants, as normal use might involve more than one dose or higher concentrations of cannabidiol. Additionally, while a two-hour waiting period was followed to account for maximum absorption post-consumption, in some participants, the full effect of cannabidiol might not have been achieved when the driving simulation test was performed.

Conclusions

To summarize, the current study explored the impact of cannabidiol and drowsiness induced by its use on the driving performance of healthy adults.

While no significant difference in the simulated driving performance of participants in the cannabidiol treatment and placebo groups was reported, cannabidiol recipients performed slightly worse on all measured outcomes.

Larger clinical trials with repeated doses of cannabidiol that reflect its normal usage might be needed in the future for conclusive results.