1. Experimental studies on cannabis and driving impairment

The aim is to evaluate the current evidence on the association between acute cannabis intoxication and driver impairment.

Consensus cannabis expert working group.

1) To what extent does cannabis impair driving? Cannabis can impair driving performance, particularly at higher doses. 2) How long after using cannabis are you safe to drive? There is no ‘magic number’ for when it is safe to drive after cannabis intake. Cannabis affects different people in different ways, and the time needed to recover from cannabis intoxication is not fixed. 3) Is everyone who uses cannabis impaired? Cannabis is an impairing psychoactive drug. The duration and magnitude of effects varies based on numerous factors, such as an individual’s history of cannabis use (e.g., light, moderate, and chronic frequent users) and the method of administration (e.g., smoking, vaping, or oral ingestion). 4) How does cannabis compare with alcohol While there are similarities in the effects of alcohol and cannabis on driving, the two drugs produce distinct behavioural effects. Unlike cannabis, alcohol tends to decrease inhibition, inflate self-confidence, and increase risk-taking behaviour. While cannabis does impair several important driving related skills, cannabis is often associated with slower driving, increased headway, and a reduced willingness to drive. These results suggest a heightened awareness of impairment and potential compensatory mechanisms but do not preclude control decrements.

While experimental studies provide important insight into the impairing effects of cannabis on driving performance, further research is needed to evaluate factors that may moderate THC’s effects on driving.