A new study conducted by Australian and Dutch research experts and published in JAMA looked at how CBD impacts driving, and it found that while THC can definitely cause driving impairment issues, there is not yet any evidence that CBD alone can.

“With rapidly changing attitudes towards medical and non-medical use of cannabis, driving under the influence of cannabis is emerging as an important and somewhat controversial public health issue,” said Iain McGregor of the University of Sydney, who worked on the study. “While some previous studies have looked at the effects of cannabis on driving, most have focused on smoked cannabis containing only THC (not CBD) and have not precisely quantified the duration of impairment.”

As cannabis legalization sweeps the nation, CBD is becoming very widely accepted. It is legal across the U.S., and many use CBD products often for pain relief, even if they don’t use THC because it is illegal or they don’t want the high, so this is very important information to have access to.

The Study

The study looked at how CBD impacts driving when faced with real-world conditions. It also compared driving on CBD to driving without taking CBD, to driving only on THC, and to driving on a combination of THC and CBD.

For the test, participants drove on the highway 40 minutes after vaping, and then again four hours after that. They were then tracked to see how much they swerved or weaved in their lanes, and how well they maintained driving in a straight line while under the influence of THC or CBD, or, in some cases, without either. 

When analyzed, the results showed that there was no difference in driving impairment between being sober and having vaped CBD only 40 minutes ago. However, the study did detect mild impairment associated with THC and CBD combined, and with THC only.

“These findings indicate for the first time that CBD, when given without THC, does not affect a subject’s ability to drive,” said Thomas Arkell, the study’s author.  “That’s great news for those using or considering treatment using CBD-based products.”

This study was also significant for another reason. It didn’t detect any impairment at all four hours after vaping, even when THC was involved. Studies in the past have shown that three hours is the length of time that users will be impaired from cannabis after smoking or vaping, if THC was involved, and this further backs that up. 

This is very important, and underscores that roadside cannabis tests that can detect cannabis hours or even days after smoking are not a fair gauge of whether or not a drive is impaired behind the wheel. In some cases, cannabis can even take weeks to metabolize.

“Road safety is a primary concern,” says Arkell. “These results should allow for evidence-based laws and regulation for people receiving medical cannabis.”

While this is by no means the final word when it comes to cannabis and driving, and a lot more research needs to be done, this provides crucial support for the ideas that CBD does not impair drivers, and that THC only impairs drivers for about three hours after use.

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