Under the Hood

Is It Safe To Drive While High On Marijuana?

In a new study involving nearly 800 medical cannabis users in Michigan, researchers reported that around half of all participants admitted to driving while "a little high" while about a fifth of them, said they have been "very high" at some point while driving.

"To know that folks are driving and may be impaired from using their medical marijuana is concerning from a public health perspective," said lead author Erin E. Bonar, Ph.D., a licensed clinical psychologist and assistant professor at the University of Michigan.

It is understandable that many would see read these findings and have concerns about safety. While we can all agree that drunk driving is a bad idea, just how safe is it to drive while high? The answer is not very clear as far as literature goes.

The level of risk is tied to how high a person is at the time, measured by their tetrahydrocannabinol (THC) blood level. The legal limit in most states specifies that drivers with five nanograms of active THC in their blood can be prosecuted for driving under the influence. 

Stephen Talpins, an attorney and highway safety expert, is among those who are in favor of a zero-tolerance standard. "There should be zero tolerance for people driving with any amount of THC in their blood," Talpins told the Washington Post, noting that the current standard is "a license to use with near impunity."

On the other hand, Mark A.R Kleiman, a professor at New York University, stated that driving while high should be treated as a traffic infraction rather than a crime unless the driver goes over the speed limit or shows signs of aggression and recklessness. 

This is because the aforementioned THC blood level testing is not a very accurate way to measure how impaired a person is. Traces of the drug can be detected long after the "high" has passed and can remain in the system for as long as a month. Indeed, there is no equivalent test for cannabis as reliable as breath alcohol detection tests. 

While this presents a limitation for research, we do know that marijuana can affect cognitive abilities that play a role in driving, attention, motor coordination, reflexes, etc. At the same time, researchers have found mixed results when examining any possible link between cannabis use and the risk of road accidents.

Past studies have also suggested that people who are high are more aware of their impairment than people who are drunk. While the latter is likely a poorer judge of how intoxicated they are, marijuana users may drive slower and relatively be more careful.

For now, most researchers would say that driving while high is safer than driving while drunk. But driving when you are sober is definitely the safest option, until further research emerges.