Fifty-six percent of those who take medical marijuana for chronic pain admit that in the last six months they've driven under the influence of marijuana within two hours of using it.

About one in five report that they've driven while "very high" at least once in the last six months, and about half say they've driven while "slightly high."  

That's according to a recent University of Michigan study of almost 800 Michiganders who were applying for medical marijuana re-certification or a new certification for chronic pain in 2014 and 2015.

Lead author Erin Bonar, Ph.D., assistant professor of psychiatry and a clinical psychologist at the UM Addiction Treatment Services, said, "Those percentages don't add up to 100% because they are separate questions. These people overlap. They could have said yes to all three questions."

Bonar said mixing marijuana and driving is risky.

"Using marijuana can result in changes in your reaction time, how well coordinated you are, and we need those functions when we're driving to respond to unexpected events," said Bonar.

Read the full article at Michigan Radio.