Medical marijuana is currently legal in more than 30 states including Pennsylvania. Do those who use the drug legally pose a danger on the highways?

A new study of patients who use medical cannabis to treat chronic pain finds more than half say they’ve driven under the influence in the past six months,

“We know that using marijuana can affect things like your coordination, or your reaction time and those are critical functions for driving,” said  Erin Bonar, PhD,  University of Michigan Addiction Center, author of the study.

The study at the University of Michigan Addiction Center surveyed nearly 800 medical cannabis users. It found 51 percent reported driving a little high,  while 21 percent  drove very high.

Dr, Bonar recommends no driving at all after using cannabis, or waiting several hours before getting behind the wheel.

She explained, “We just don’t know how long the amount a person uses is going to be in their system and affect their driving. We know things about how alcohol affects our body, how much I can drink at this body weight over what period of time, and that is pretty standardized. We just don’t have that information yet for marijuana.”

With no gold standard yet for determining how high a person is or how impaired they are from marijuana, researchers are developing marijuana breathalyzers and other roadside tests.  

Studies show marijuana is in the body longer than it’s in the brain so researchers say even if  a person doesn’t feel high in the moment, it can still be affecting them.