Long after the high dissipates, marijuana use can still make even sober users worse, more dangerous drivers, a new study suggests.
Researchers at McLean Hospital and Harvard University found that people who used marijuana heavily and on a long-term, recreational basis drove faster, ran more red lights and got int more accidents in a driving simulator than did others.
The earlier the participants had started using pot, the worse their driving was.
Although their study didn’t explore the underlying brain changes in these individuals, the scientists speculate that the drug may change neural wiring to make people maker more rash decisions and behave more impulsively.
High drivers and the effect of legal weed on road safety are a growing concern in the US, where marijuana is now legal for either recreational or medicinal use in 33 states.
New research suggests that marijuana’s long-term effects on the brain may make chronic recreational users worse drivers even when they’re sober (file)
Already these states where pot is legal are facing challenges in establishing what constitutes and how to quantify when someone is too high to drive.
But the link between legal weed and sdagnerous driving is hard to deny.
Collectively, Colorado, Oregon and Washington saw an average 5.2 percent jump in car crashes after recreational marijuana was legalized.
Another study published in February found that there were about 170 extra road deaths in the months after the ban on pot was lifted.
Arbitrary though the the basis for the legal limit on blood alcohol levels is in the US, it’s easy enough to measure via breathalzyer.
But weed is metabolized differently and has less consistent effects on each user. It remains in the body for much longer before breaking down, so blood and urine tests struggle to pick up how much someone has used and how recently.
That may also have something to do with why it affects the brain differently in the long run.
Researchers at the University of Illinois, Chicago, found evidence in 2018 that marijuana may alter the development of the prefrontal cortex in adolescents.
This part of the brain drives decision-making, planning and self-control.
And the McLean researchers believe those changes may be long-lasting and lead to bad driving into adulthood and after the high has faded.
They had study participants get behind the simulator wheel at least 12 hours after they’d ingested or smoked pot and when they showed no signs of intoxication.
Some of the test drivers were chronic users and some had started even before the age of 16, while others were casual or never-users.
The differences emerged quickly.
Cannabis users were speed demons with a penchant for running red lights, compared to their peers who didn’t partake.
Tokers were also more prone to swerving and crossing over into neighboring lanes.
And those who started smoking weed regularly before they turned 16 were the worst offenders, scoring more poorly on their simulated driving tests.
‘People who use cannabis don’t necessarily assume that they may drive differently, even when they’re not high,’ said the study’s senior author, Dr Staci Gruber, who’s spent much of her career studying marijuana’s cognitive effects.
‘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.
‘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.’
But Dr Gruber was careful to note that her study’s findings don’t mean that marijuana can’t be used responsibly, especially by medical card holders, for whom it may have considerable benefits.
‘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,’ she said.