More than half of people who take medical cannabis for chronic pain say they’ve driven under the influence within two hours of using it at least once in the last six months.
One in five of them said they’d driven while “very high” in the past six months, researchers report.
The results of the survey of 790 Michigan medical cannabis users are troubling, says Erin E. Bonar, assistant professor of psychiatry and a practicing clinical psychologist at University of Michigan Addiction Treatment Services and lead author of the paper, which appears in Drug & Alcohol Dependence.
Hundreds of thousands of Americans have state approval to use medical marijuana, including nearly 270,000 in the state of Michigan, according to Statista, as of May 2018. Michigan is second only to California for the highest number of medical marijuana patients in a state.
Bonar says that when people drive under the influence of marijuana their reaction time and coordination may slow down and they could have a harder time reacting to the unexpected. If they are in a risky situation, they could be more likely to be in a motor vehicle crash, because they wouldn’t be able to respond as quickly.
Researchers surveyed Michigan adults seeking medical cannabis recertification or a new certification for chronic pain in 2014 and 2015. The researchers asked about respondents’ driving habits for the past six months.
Fifty-six percent of participants reported driving within two hours of using cannabis, 51 percent reported they drove while a “little high,” and 21 percent reported driving while “very high.”
“There is a low perceived risk about driving after using marijuana, but we want people to know that they should ideally wait several hours to operate a vehicle after using cannabis, regardless of whether it is for medical use or not,” Bonar says. “The safest strategy is to not drive at all on the day you used marijuana.”
How impaired are you?
Researchers aren’t sure how marijuana affects driving for chronic daily users, who might have longer-lasting effects that linger in their system.
To add complexity to the issue, Michigan voters approved the use of recreational marijuana in November. In early December, it became legal under state law for any Michigan resident over the age of 21 to use marijuana inside a private residence, and to grow up to 12 plants for personal use. Marijuana use and possession remains illegal under federal law.
In light of this policy change, all cannabis users need a clear understanding of the side effects of this drug, Bonar says.
“When it comes to driving, we haven’t yet figured out the best way to know how impaired marijuana users are at any given time,” she says. “With alcohol, you can do some quick math based on the amount you drank, and take an educated guess at your blood alcohol level.
“For marijuana, an estimate like this would be complicated. It’s hard to quantify because there is a lot of variation in marijuana dosing, THC potency, and route of administration. We also don’t have specific guidelines yet about when exactly it would be safe to operate a vehicle.”
The goal of the study—conducted before the ballot question that resulted in the change in state law passed—is to help medical marijuana users drive more safely.
“We believe more research is needed to inform a larger public education effort that will help individuals understand the risks for themselves, and others, of driving while under the influence of cannabis,” she says.
“It is especially needed during this time of rapid policy change as many states are determining how to manage marijuana legalization. We also need clearer guidelines about marijuana dosing and side effects with an understanding of how individual differences in things like sex and body weight interact as well.”
Source: University of Michigan