Cannabis Edibles, Blood THC Levels, and Their Impact on Driving Impairment Regulations

By
José Ignacio Nazif-Munoz
August 31, 2026

Jama Network Open

Objective:

To assess the impact of legally available Canadian cannabis edibles on simulated driving performance and evaluate the implications for cannabis-impaired driving laws.

Approach:

Study Design: A randomized, double-blind, placebo-controlled crossover trial was conducted with adults who regularly use cannabis.
Endpoints: Primary endpoint was standard deviation of lateral position; secondary endpoints included additional driving-performance measures and subjective effects.

Key Findings:

THC edibles caused dose-dependent deterioration in simulated driving performance.
Blood THC concentrations remained at or below commonly applied legal thresholds despite observed performance impairment.
The pharmacokinetic profile of edible cannabis complicates the interpretation of biological measures of impairment.

Interpretation:

Current models may not accurately reflect the relationship between THC levels and driving performance.

Limitations:

Laboratory simulators cannot fully replicate real-world driving conditions.
Current enforcement frameworks may not adequately account for the complexities of cannabis impairment.

Conclusion:

Future research should focus on defining circumstances of meaningful impairment and exploring a wider range of driving behaviors affected by cannabis.