Smoking lots of weed can make you a bad driver – even when you’re not high, study says

Smoking a lot of marijuana can make you a bad driver, even when you’re not high, according to a study.

Heavy, chronic cannabis users had poorer driving performance than non-users in a study published by researchers at McLean Hospital, an affiliate of Harvard University, according to a news release.

The study also linked worse driving to people who began smoking marijuana before age 16.

Marijuana users who hadn’t smoked for at least the past 12 hours hopped into a driving simulator for the study.

The results?

They hit more pedestrians, drove over the speed limit, blew past more stop lights and crossed over the center line more often, according to the study.

“People who use cannabis don’t necessarily assume that they may drive differently, even when they’re not high,” said Staci Gruber, the lead author of the study. “We’re not suggesting that everyone who uses cannabis will demonstrate impaired driving, but it’s interesting that in a sample of non-intoxicated participants, there are still differences in those who use cannabis relative to those who don’t.”

In the study, heavy marijuana use meant at least five times a week and at least 1,500 times overall, CNN reported.

According to the National Institute on Drug Abuse, marijuana is the drug found most frequently in drivers involved with crashes.

NBC reported that the number of fatal crashes when drivers had cannabis in their systems doubled from 2007 to 2016, according to the National Highway Traffic Safety Administration.

“It didn’t surprise us that performance differences on the driving simulator were primarily seen in the early onset group,” said Mary Kathryn Dahlgren, another author of the study. “Research has consistently shown that early substance use, including the use of cannabis, is associated with poorer cognitive performance.”

This story was originally published January 15, 2020 at 1:56 PM.