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Marijuana affects consumers' driving even after the high has faded

Researchers are warning recreational marijuana users about getting behind the wheel

Photo (c) rclassenlayouts - Getty Images
Recent studies have shown how recreational marijuana use has affected consumers’ driving habits. Now, a new study conducted by researchers from McLean Hospital found another surprising fact about driving after drug use. 

The study revealed that consumers’ driving could be negatively affected by marijuana use, even after the effects of the drugs have worn off. 

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

How driving is affected

To see how using marijuana affected participants’ driving ability when they weren’t high, the researchers had both regular marijuana users and those who didn’t use the drug participate in the study. 

The participants’ driving skills were put to the test in a simulator that mimicked real-world conditions. Participants also answered questions about their marijuana use, including how often they used the drug and when they initially started using it. At the time of the experiment, the group of regular marijuana users were clean of the drug for 12 hours and were completely sober. 

The researchers learned that despite not feeling any effects of the drug, the group of marijuana users didn’t perform as well on the driving simulator as those who had never used the drug. Simple road rules, such as following speed limits or stopping at red lights, weren’t followed as closely by the group who used marijuana. 

The researchers took the test a step further by looking at when the participants had first started using marijuana so they could determine what effect that had on their driving abilities. They learned that the longer the participants had been using the drug, the more dangerous their driving was. 

Though the researchers did explain that marijuana can affect everyone differently, they said the primary goal for every driver is to be safe and ensure that they’re fit to get behind the wheel.

“There’s been a lot of interest in how we can more readily and accurately identify cannabis intoxication at the roadside, but the truth of the matter is that it is critical to assess impairment, regardless of the source or cause,” said Dr. Gruber. 

“It’s important to be mindful that whether someone is acutely intoxicated, or a heavy recreational cannabis user who’s not intoxicated, there may be an impact on driving, but certainly not everyone demonstrates impairment simply as a function of exposure to cannabis. This is especially important to keep in mind given increasing numbers of medical cannabis patients who differ from recreational users with regard to product choice and goal of use.” 

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