Cannabis Edibles Had Minimal Effects on Simulated Driving Despite Feeling Intoxicating for 7 Hours

Cannabis edibles produced a decrease in mean speed at 2 hours post-consumption but not at 4 or 6 hours. No changes were found in weaving (SDLP), maximum speed, speed variability, or reaction time at any time point. Blood THC peaked at ~2.8 ng/mL at 2 hours. Driving impairment was not correlated with blood THC levels. Participants felt subjectively intoxicated for 7 hours and were less willing to drive for up to 6 hours.

Counterbalanced crossover study with cannabis edible and no-THC/CBD control sessions. Participants drove a driving simulator before and after consuming their preferred legally purchased edible (mean 7.3 mg THC). Blood THC and metabolites were measured. Standard and dual-task driving assessments at 2, 4, and 6 hours.

This is the first study of cannabis edibles and driving. Current legal THC driving limits are based on smoked cannabis research. Edibles produce lower blood THC levels but longer subjective intoxication, creating a mismatch between how impaired users feel and what objective driving measures show.

The disconnect between subjective intoxication (7 hours) and objective driving impairment (2 hours, speed only) raises complex policy questions. Current blood THC limits may not capture edible-related impairment accurately, and relying on driver self-assessment may overestimate actual impairment from edibles.

Driving simulator does not replicate all aspects of real-world driving. The mean dose (7.3 mg) was below the maximum single-package limit, so higher doses may produce more impairment. Individual tolerance varies widely. Small sample typical of driving simulation studies.