An alarming new study suggests many medical marijuana users have driven under the influence.
Researchers at the University of Michigan surveyed nearly 800 medical marijuana users.
Over half reported driving within two hours of taking the drug.
Also, more than 20 percent reported they were "very high" when they were behind the wheel.
Experts say a driver's reaction time may be impacted if they are under the influence.
The study involving 790 medical marijuana users in Michigan was taken before voters approved the use of recreational marijuana in the state this past November.
That law, which allows any Michigan resident over the age of 21 to use marijuana inside a private residence, became legal in December.
This study was led by researchers at the University of Michigan Addiction Center and published in Drug & Alcohol Dependence.