Grant: Project Grant

Background: Cannabis impairs driving performance but most research involves recreational cannabis. Cannabis may not be dangerous for supervised medical cannabis patients (SMCPs) who take it with physician supervision. SMCPs are older, use lower doses of THC and may develop tolerance. We will use a driving simulator to study how cannabis impacts driving performance in SMCPs who take cannabis for pain, sleep, anxiety or depression. Methods: SMCPs will drive a simulator, complete cognitive tests and have blood THC and CBD levels measured. To assess long-term changes in driving performance, SMCPs will drive a simulator before cannabis therapy and at 1 and 4 months after starting. We will examine how driving performance changes after starting cannabis therapy and whether SMCPs who use prescribed cannabis with high vs low THC content perform differently. To assess acute impairment, we will examine whether driving performance changes immediately after inhaling or ingesting prescribed cannabis containing THC. SMCPs will drive a simulator before and ½, 2, 4, and 6 hours after taking their prescribed THC-containing cannabis. We will compare their driving before and after cannabis use. We will also assess whether SMCPs who inhale vs ingest cannabis perform differently. Finally, we will identify risk factors for driving impairment (e.g. age, sex, gender, THC dose, use of other medications). We will use statistical models to assess whether these factors are related to driving performance. Outcomes: This will be the first large study of the effect of cannabis on driving performance in SMCPs. The results will help SMCPs understand when it's safe to drive after using cannabis. It will also help healthcare providers advise SMCPs about driving and identify patients at risk of driving impairment. This research is also relevant for people who set traffic policy because we will show how often SMCPs have THC above legal limits and whether this is related to driving performance.