22 Sep Cannabis Edibles Impair Driving at Doses Below Legal Enforcement Thresholds
Notice: If you or someone you know needs help with substance use, contact SAMHSA at 1-800-662-4357 (free, confidential, 24/7) or visit findtreatment.gov. Do not drive after consuming cannabis or any substance that may impair your ability to operate a vehicle safely.
Dr. Bernard Le Foll
MedicalResearch.com Interview with:
Dr. Bernard Le Foll, MD, PhD
Chair in Addiction Psychiatry, Department of Psychiatry, University of Toronto
Head, Translational Addiction Research Laboratory, Campbell Family Mental Health Research Institute
Cannabis edibles — cannabis products that are ingested rather than smoked — are widely available and increasingly consumed, yet their effects on driving performance have been far less studied than smoked cannabis. A new randomized clinical trial published in JAMA Network Open now provides the first systematic evidence on how edibles affect simulated driving, and the findings have significant implications for road safety and impaired driving enforcement. According to NIDA (National Institute on Drug Abuse), cannabis is one of the most commonly detected substances in drivers involved in motor vehicle crashes, and understanding the full duration and dose-dependence of impairment — including from non-smoked forms — is critical to effective public safety policy.
Watch the Video presentation of this study on YouTube
MedicalResearch.com: What is the background for this study? What are the main findings?
Dr. Le Foll: It is known that smoked cannabis can impair driving performance. However, the impact of cannabis edibles — cannabis that can be ingested — was not studied. There have been limited studies on even the pharmacokinetic and subjective effects of edibles, and no studies had been performed on their impact on driving when we designed this study. We found that edibles at 10 and 20 mg clearly impact driving performance. The effect is also long lasting. This has significant implications for individuals who consume edibles and plan to drive.
MedicalResearch.com: What are the implications for assessing impaired driving?
Dr. Le Foll: We found that the impairment was observed at doses that were below the per se threshold limit that is currently used for enforcement. It would be important to develop methods to assess how to determine impairment at the roadside taking this into consideration.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Dr. Le Foll: The most important next step is to develop reliable methods for detecting driving impairment from edibles at the roadside. Because current per se thresholds may not capture the impairment we observed at these doses, enforcement tools need to be reassessed in light of this evidence. Future research should also examine the duration of impairment more precisely, as the long-lasting nature of the effect we observed is particularly relevant for public safety guidance.
MedicalResearch.com: Is there anything else you would like to add?
Dr. Le Foll: The study was funded by Public Safety (grant to Dr. Le Foll and Dr. Brands). Indiva provided the placebo edibles at no cost.
Citation:
Le Foll B, Matheson J, Antwi P, et al. Dose-Dependent Effects of Cannabis Edibles on Simulated Driving Performance: A Randomized Clinical Trial. JAMA Netw Open. 2026;9(8):e2631306. doi:10.1001/jamanetworkopen.2026.31306
For a broader overview of what the research shows about cannabis impairment, driving safety, and how per se legal thresholds compare to measured impairment, see this MedicalResearch.com overview of cannabis and driving — what the research shows.
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Last Updated on September 23, 2026 by Marie Benz MD FAAD