According to a new study by researchers at McGill University in Montreal, drivers who smoked marijuana could be impaired for as much as five hours after their last hit.
The study found that drivers were able to complete simple tasks like braking and maintaining a steady speed on the road but those high on weed were “significantly” more at risk for a crash.
Per the Montreal Gazette, “When we added distractions and (the) tasks required more attention and more focus and cognitive skills like divided attention … response time was much greater,” study co-author Dr. Tatiana Ogourtsova remarked. “We call them complex tasks, but they are things one has to do in everyday driving, which involves a lot of divided attention.
“I think the five hours maybe came as a surprise. We thought maybe the effects would not be as strong. But they were very significant.”
There were 45 people from ages 18 to 24 in the study who are “recreational cannabis users.” They were asked to complete different driving tasks before smoking marijuana and then did the tests one hour after smoking, then three hours after and finally five hours after their last hit from a joint.
“Performance was almost always significantly better without cannabis,” the study found. “The only exception was for vigilance at 1 hour after cannabis use: vigilance was higher at that time point than for the non-cannabis state. This finding is congruent with the findings of others who have reported an increase in vigilance or caution among participants who drove after cannabis use.”
