Beta-myrcene, a common cannabis terpene, significantly reduced speed control and increased divided attention errors on a driving simulator, even without cannabinoids.
Impaired driving researchers, traffic safety policymakers, and cannabis pharmacology scientists.
n=10 crossover studyshowing beta-myrcene impaired speed control and divided attention on driving simulator
What the researchers found
Beta-myrcene at 15 mg produced statistically significant reductions in speed control and increased errors on a divided attention task in a driving simulator, providing proof-of-principle that terpenes can impair driving.
Why it matters
Cannabis-impaired driving research has focused almost exclusively on THC. This study shows that other cannabis compounds may contribute to driving impairment independently.
The numbers in context
n=10 participants in crossover design. 15 mg pure beta-myrcene vs. canola oil control. Significant reductions in speed control. Significant increased divided attention errors. Baseline and three follow-up blocks.
How the study worked
Double-blind, placebo-controlled, crossover pilot study using STISIM driving simulator with 15 mg pure beta-myrcene capsule versus canola oil control.
Who was studied
10 participants in a controlled crossover design.
What this study cannot tell us
Very small sample (n=10). Single terpene dose tested. Simulated driving may not reflect real-world driving. 15 mg may not represent typical exposure from cannabis use.
How to read the evidence
Double-blind crossover design is rigorous but extremely small sample limits confidence in findings.
When this study was published
Recent pilot study — first to test terpene effects on driving performance.
The bigger picture
If cannabis terpenes independently impair driving, current impaired driving assessments focused solely on THC may underestimate cannabis-related driving risk.
Replication
Very small pilot (n=10); larger studies with multiple doses essential.
Funding
Not specified in abstract
Conflicts of interest
Not specified in abstract
Questions still open
- Do terpenes and THC have additive or synergistic effects on driving impairment?
- Should terpene content be considered in cannabis product labeling for driving safety?
Read the original research
The Effects of β-myrcene on Simulated Driving and Divided Attention: A Double-Blind, Placebo-Controlled, Crossover Pilot Study.
Cannabis (Albuquerque, N.M.), 6(1), 9-19
Citation
Johnson, Mark B; McKnight, Scott; Taylor, Eileen P; Mechtler, Laszlo; Ralyea, Christopher C. (2023). The Effects of β-myrcene on Simulated Driving and Divided Attention: A Double-Blind, Placebo-Controlled, Crossover Pilot Study.. Cannabis (Albuquerque, N.M.), 6(1), 9-19. https://doi.org/10.26828/cannabis/2023.01.002