CBD Driving Non-Inferiority Was Established for Some Comparisons, Not All
A small CBD driving study found no significant cognitive impairment, but some driving comparisons remained inconclusive under its non-inferiority analysis. ‘No significant difference’ and ‘demonstrated non-inferiority’ are not interchangeable conclusions.
A predefined margin made the question explicit
Seventeen healthy adults completed placebo and 15, 300 and 1,500 mg oral CBD sessions in a blinded crossover trial. Simulated drives included standard and car-following components at two post-dose assessments.
The main analysis asked whether CBD increased lane-position variability by more than a predefined margin. The margin was informed by alcohol-related performance research; participants were not being diagnosed as having an equivalent blood alcohol concentration.
Evidence depended on the drive component
Non-inferiority was established for the first standard-drive component and the second car-following component across CBD doses. The second standard-drive comparison also met the criterion at 15 and 1,500 mg.
Other comparisons were inconclusive because confidence intervals included both no difference and the non-inferiority boundary. That is uncertainty, not demonstrated impairment. Conversely, it cannot be rewritten as proof that a clinically relevant difference was excluded in every condition.
Keep other null outcomes separate
No CBD dose significantly impaired the measured cognitive outcomes or induced reported intoxication. Those results add context but do not replace the confidence-interval analysis for the primary driving measure.
The small sample, simulator setting and single-dose design limit conclusions about all users and everyday driving. The study supports a generally reassuring pattern for pure oral CBD under its conditions, while preserving uncertainty in specific comparisons. It does not validate THC-containing oils or establish that every CBD product is suitable before safety-sensitive activity.
Related: Why concentrations do not establish functional impairment.
Primary research
Effects of cannabidiol on simulated driving and cognitive performance: A dose-ranging randomised controlled trial. Journal of Psychopharmacology (Oxford, England) (2022).
