WATERLOO, ON, JUNE 27, 2017 – Canadians for Fair Access to Medical Marijuana (CFAMM), a national non-profit organization, released a first-of-its-kind preliminary research review on medical cannabis impaired driving – one of the major public safety concerns stemming from the legalization of non-medical cannabis.

The review situates the use of cannabis for medical purposes among research related to policy, prevalence, and risk of cannabis/THC impaired driving. The 200,000 legally authorized Canadians who are prescribed medical cannabis have important and distinct characteristics including dosing, strains, tolerance, methods of administration, and education received by their prescribing physicians. These factors, explored in the review, set medical cannabis patients apart from non-medical consumers and demonstrate this to be a key area left unexplored in previous impaired driving literature.

This preliminary review offers insight into how cannabis used for medical purposes relates to impaired driving, including the following topics:


While CFAMM is fully against impaired driving and supports responsible driving legislation, the term “impairment” is widely used but is not always clearly defined. When speaking of impairment, crucial to this dialogue is speaking to actual impairment of cognitive, psychomotor, and other functions necessary to safely drive – not simply a measure of previous use such as the presence of THC in blood. Unlike blood alcohol concentration, which is scientifically linked to levels of impairment, matching levels of impairment to levels of THC in one’s system is still widely debated and has not been studied related to medical cannabis use.


Although many studies have explored the risk of recreational or occasional use of cannabis related to driving impairment, few have studied the risk related to responsible medical use of cannabis. For most patients, the goal of medical cannabis use is not to experience its psychoactive effects, but rather to treat or manage symptoms of an illness using the smallest effective dose. Although it’s a limited example, a past study on the medical use of cannabis (Sativex) for multiple sclerosis identified better driving safety measures after the introduction of cannabis in patients’ treatment regimens, suggesting a need for further research on medical users. It is also important to note that U.S. states have recorded an 8-11% drop in overall traffic fatalities one year following the introduction of medical cannabis legislation.


Many medically authorized Canadians use cannabis daily or near daily to manage symptoms associated with their illness and are expected to follow advice from health care providers. This includes safe-use guidelines, such as waiting 4+ hours after consumption before driving, to help eliminate risk of potential impairment. The metabolism and effects of THC are highly variable from person-to-person and THC can remain detectable within a regular user’s blood for days after last consumption. The government’s proposal, which would set a per se cut-off of 2ng/ml THC at the lower end, means even when patients are not impaired, they would have to stop using their medicine for 3-7+ days before driving.


“Although driving is not a right but a privilege, patients who use cannabis responsibly and are not impaired should still be able to drive without risk or fear of being charged. It is necessary for the government to incentivize further research and include considerations for patients using cannabis. While a strict precautionary approach may be appropriate in light of limited evidence, policymakers have a responsibility to both safeguard road safety and balance the rights of medical cannabis patients to ensure they are not unfairly criminalized by drugged driving laws that do not target impairment.”

-Jonathan Zaid, Lead Author and Executive Director, CFAMM

For interview requests, contact us here. Stay tuned for the full, bilingual report and policy recommendations in the coming months.

En Français »