2022 | United States | Randomized placebo-controlled trial
Marcotte TD et al. JAMA Psychiatry. 2022;79:201-209.
Methods: Investigators randomized 191 regular cannabis users to smoke placebo or cannabis with either of two THC concentrations. They compared driving simulator performance and perceived readiness to drive at repeated intervals.
Findings: THC impaired simulator performance at 30 and 90 minutes. Many participants reported increased readiness to drive at 90 minutes even though measured performance had not recovered from the earlier impairment.
Limitations: A simulator and a selected population of regular users do not represent all road conditions or users. Smoked cannabis results do not define edible effects. Group averages cannot establish a safe driving interval for an individual.