Driving Simulator: THC Dosing Associated with Decreased Speed, No Residual Effects on Performance

Toronto, Canada: Subjects typically decrease their driving speed, but demonstrate few other significant changes following cannabis inhalation, according to clinical data published in the journal Drug and Alcohol Dependence.

A team of Canadian investigators assessed simulated driving performance in a group of young adult subjects who had consumed cigarettes containing either high-THC, low-THC, or placebo (no THC). Participants in the trial were regular users of cannabis. Subjects’ performance was analyzed 30 minutes after dosing, and then again 24 hours and 48 hours later.

Authors reported, “Smoked cannabis (12.5 percent THC) led to an acute decrease in speed in young adults,” a finding that is consistent with prior research. They added: “There was no clear effect of smoked cannabis on lateral control. … There was no evidence of residual effects … over the two days following cannabis administration.”

They concluded, “Among young regular but non-dependent cannabis users, smoked cannabis led to a significant reduction in driving speed, …but there was little evidence of residual effects.”

Separate studies have previously reported that repeated cannabis exposure is associated with either partial or even full tolerance among subjects in particular domains, including cognitive and psychomotor performance.

For more information, contact Paul Armentano, NORML Deputy Director, at: paul@norml.org. Full text of the study, “Acute and residual effects of smoked cannabis: Impact on driving speed and lateral control, heart rate, and self-reported drug effects,” appears in Drug and Alcohol Dependence. Additional information appears in the NORML fact-sheet ‘Marijuana and Psychomotor Performance.’