A new study claims that cannabis that is high in CBD does not appear to impair people’s driving. Swiss researchers gave 33 participants joints that contained 500mg of tobacco plus either 500 mg of CBD-rich cannabis or 500 mg of a placebo. After the participants smoked these joints, they administered common tests for determining if someone is too impaired to drive.

The results show the participants’ reaction time wasn’t any different if they had smoked the CBD-rich cannabis or the placebo. The researchers
tested the participants in multiple ways to confirm they were not impaired.

“The results revealed no significant differences between the effects of smoking CBD-rich marijuana and placebo on reaction time, motor time,
behaviour under stress, or concentration performance,” the authors wrote.

Though the cannabis was high in CBD, it also contained THC. The participants had the level of THC in their blood tested and were found to be above what is typically considered the legal limit, but this did not impact their driving in any noticeable way.

“Although the observed levels of free THC concentrations have been reported to cause symptoms of impairment in previous studies in which THC-rich marijuana was smoked, no signs of impairment were found in the current study,” the authors wrote. “This finding suggests that higher CBD concentrations cause a negative allosteric effect in the endocannabinoid system, preventing the formation of such symptoms. Nevertheless, it is recommended that consumers refrain from driving for several hours after smoking CBD-rich marijuana, as legal THC concentration limits may be exceeded.”

It may be that having high levels of CBD in a cannabis product helps reduce the impairment that may be caused by consuming THC. Other studies have come to similar conclusions, but it’s not yet fully clear how levels of CBD in a cannabis product may change the effects of THC. The authors said more research still needs to be done.

This kind of research is important because many states that have legalized cannabis have set a limit on how much THC can be in someone’s system before they’re considered too impaired to drive, and the science has consistently shown that these levels of THC do not actually represent impairment. It’s also important because in many states with medical cannabis someone can be arrested for driving with some level of THC in their blood even if they haven’t consumed cannabis recently.