Experts at the University of Sydney have demonstrated for the first time that cannabidiol (CBD) does not impair a person’s ability to drive. The research is particularly relevant as CBD is increasingly used to treat anxiety, epilepsy, fibromyalgia pain, sleep disorders, and other medical issues.
“These findings indicate for the first time that CBD, when given without THC, does not affect a subject’s ability to drive. That’s great news for those using or considering treatment using CBD-based products,” said study lead author Dr. Thomas Arkell.
For the investigation, 26 participants were given four different types of vaporized cannabis in a random order on four separate occasions. The vaporized cannabis contained either: mainly THC, mainly CBD, a combination of THC and CBD, or a placebo cannabis with no active components. The amount of THC inhaled by the volunteers was potent enough to induce strong feelings of intoxication.
The driving tests that followed were conducted on a 100-kilometer stretch of public highway in a dual control car with a driving instructor present. The study participants completed two driving tests, which were conducted 40 minutes and four hours after inhaling the cannabis vapor. The researchers used a well-established scientific test that measures lane weaving, swerving, and overcorrecting.
The study revealed that cannabis containing mainly CBD did not impair driving, while cannabis containing THC caused mild impairment 40 minutes later. The individuals who were given THC no longer showed signs of impairment four hours after exposure.
“With cannabis laws changing globally, jurisdictions are grappling with the issue of cannabis-impaired driving,” said Dr. Arkell. “These results provide much needed insights into the magnitude and duration of impairment caused by different types of cannabis and can help to guide road-safety policy not just in Australia but around the world.”
Dr. Arkell said that road safety is a primary concern, and that the research can support evidence-based laws and regulation for people receiving medical cannabis.
Professor Iain McGregor is the academic director of the Lambert Initiative for Cannabinoid Therapeutics at the University of Sydney.
“The results should reassure people using CBD-only products that they are most likely safe to drive, while helping patients using THC-dominant products to understand the duration of impairment,” said Professor McGregor.
“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.”
“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.”
“This is the first study to illustrate the lack of CBD effects on driving and to also provide a clear indication of the duration of THC impairment.”
The study is published in the journal JAMA.