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The results of a new two-year study at the Center for Medicinal Cannabis Research at UC San Diego suggests that not everyone can handle driving under the influence of THC. At least 50% of the control group had some impairment while undergoing driving simulations, reports NBC San Diego.
The researchers recruited 191 regular cannabis users to take part in the study, some given weed to smoke with either 5.9% or 13.9% THC, and others given the placebo. Of those with THC in their systems, about half showed diminished ability in driving tests, including swerving in lanes, not keeping their attention on the road, and following a lead car. The decline was sharpest within the first hour after smoking, with no difference after four hours. But not all users thought there was a problem.
“Although users in the THC group felt impaired and were hesitant to drive at 30 minutes, by one hour, 30 minutes they believed the impairment was wearing off and were more willing to drive,” said senior author Thomas Marcotte, co-director of CMCR and a professor of psychiatry at UCSD School of Medicine. “This was despite their performance not significantly improving from the 30-minute point. This may indicate a false sense of safety, and these first few hours may constitute a period of greatest risk since users are self-evaluating whether it is safe to drive.”
Why it’s important
As recreational cannabis use becomes legal in more states, more people will undoubtedly drive while high. And law enforcement is still trying to figure out how to measure and regulate it. Of course it’s easy to say, “Don’t smoke and drive.” But studies like this show it’s not that simple.
DUI laws, at least when it comes to cannabis, aren’t easy to create. It’s hard to know how high someone is because of so many variables, from the product used to the individual user.
“Our study of a large group of regular users underscores the complexity in understanding the relationship between cannabis intake and driving decrements, reinforces the challenges in communicating the varying level of risks associated with use and the difficulty in identifying the subset of individuals most at risk for impaired driving,” Marcotte added.
More research is needed, say the authors. They suggest future studies should address individual biologic differences, personal experience with cannabis, and how they get it in their system.