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New Study Examined Cannabis Impairment in Driving Simulation




A Toronto, Canada-based organization recently concluded tests on how cannabis impairs drivers’ ability to drive normally.

Global News reports that the Centre for Addiction and Mental Health allowed participants to smoke cannabis for 10 minutes, followed by a driving simulator. Study members were allowed to smoke as little or as much cannabis as they preferred prior to using the simulation, with the amount of THC ranging from zero to 42 nanograms per milliliter.

The simulation took participants on a nine kilometer (five-and-a-half mile) drive, going the speed limit of about 80 kilometers (approximately 50 miles) per hour. Drivers would encounter hurdles such as slow moving vehicles, or moving their own vehicle back to the center of a lane after drifting off, to test their alertness and attention while impaired.

Participants’ blood was tested 24 and 48 hours after the test concluded to check their levels of THC. While tested individuals may have still had THC in their system, they drove as they normally would. “We found significant evidence of difference in driver behaviour, heart rate and self-reported drug effects 30 minutes after smoking cannabis, but … we found little evidence to support residual effects,” the authors described of their results.

Researcher Scott Macdonald stated that some state or workplace laws that require a zero tolerance THC are “not scientific.” “I consider it one of the biggest myths about cannabis, that there are 24-hour hangover effects that are measurable,” Macdonald told Global News.  “When people smoke cannabis, they’re only impaired for a short, short period of time. You could have THC in your bloodstream, but you’re not a danger.”

According to Jenna Valleriani, executive director of Hope for Health Canada, zero tolerance policies target younger adults of legal age who still have to drive to work and school. “Driving is a privilege, but at the same time, cannabis is legal now, and young people over the age of access should be able to consume on the weekend and drive one full day later to work or school without risking a DUI charge.”