ANN ARBOR – A new study by researchers from the University of Michigan Addiction Center reveals that more than half of chronic pain sufferers who use medical cannabis in Michigan drive under the influence.
For the study, which appears in the journal Drug & Alcohol Dependence, researchers surveyed 790 Michigan medical marijuana users. Fifty-six percent of people surveyed said they have operated a vehicle within two hours of using marijuana at least once within the past six months.
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One in five people reported they'd driven while "very high." One in two people reported they'd driven while a "little high."
Related story: At a glance: The University of Michigan Addiction Center
Erin E. Bonar, the lead author, assistant professor of psychiatry at U-M and a practicing clinical psychologist at the Addiction Center, said she finds the results troubling.
"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 said in a statement. "The safest strategy is to not drive at all on the day you used marijuana."
Bonar said one's coordination and reaction time may be slowed down if he or she is under the influence of marijuana, which makes a person more at risk to be involved in motor vehicle crashes.
She added that it is still unclear how cannabis could affect the driving of chronic daily users, since the drug's effects could be longer-lasting in their system.
As of May 2018, nearly 270,000 people in the state of Michigan had approval to use medical cannabis, according to Statista. The state of Michigan has the second highest number of medical marijuana patients in the country, following California.
November's passing of the use of recreational marijuana in Michigan adds more complexity to the issue.
It is now legal for Michigan residents over the age of 21 to use cannabis inside their homes and to grow as many as 12 plants for personal use.
Due to this policy change, Bonar said the side effects of the drug should be clear to all users.
"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 said in a statement. "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, which was conducted before the November midterm elections, was to help medical cannabis users understand the risks and be safer on the roads.
"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 said in a statement.
"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."
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