Cannabidiol (CBD) may not impair people’s cognitive abilities or driving skills when taken in doses commonly used for medical purposes, a small Australian study suggests.
For the study, scientists asked 17 healthy adults to a complete a series of four driving assessments and cognitive tests after taking a placebo or CBD oil in doses of 15, 150, or 1,500 milligrams (mg). These doses represent amounts typically consumed to manage conditions like epilepsy, pain, anxiety, and sleep disorders, the researchers reported May 30 in the Journal of Psychopharmacology.
In each of these four testing scenarios, participants completed tasks between 45 and 75 minutes after taking the placebo or the dose of CBD oil, then again between 3.5 and 4 hours afterward. CBD is thought to reach peak concentrations in the blood within three to four hours after an oral dose, according to the researchers.
To demonstrate how CBD impacted driving, participants had to drive behind another vehicle at a safe distance, then navigate simulated routes on urban highways and rural roads. Scientists measured how well participants controlled the car as well as how much the vehicle weaved or drifted. They also administered cognitive tests and took blood samples to determine CBD concentrations in the participants’ plasma.
None of the CBD oil doses appeared to impair driving or cognitive performance or make participants feel intoxicated, the study found.
“Though CBD is generally considered ‘nonintoxicating,’ its effects on safety-sensitive tasks are still being established,” said the lead author, Danielle McCartney, PhD, of the University of Sydney, in the university’s press release. “Our study is the first to confirm that, when consumed on its own, CBD is driver-safe.”
Medical marijuana was legal in 37 U.S. states and the District of Columbia as of February 2022, according to the National Conference of State Legislatures. While drunk driving is illegal in every state, laws against driving under the influence of marijuana and other drugs vary from state to state; you can view them on a site produced by the Governors Highway Safety Association.
Driving while on CBD is legal in Australia and in many other countries, researchers note. The results of the new study build on earlier evidence suggesting that CBD doesn’t necessarily cause intoxication. Another cannabis component, THC, can induce sedation and a euphoric high that has been previously associated with impaired cognition.
THC can negatively impact areas of the brain that control movement, balance, coordination, memory, and judgment, according to the U.S. Centers for Disease Control and Prevention (CDC). For drivers, THC can also slow reaction times and reduce the ability to make decisions.
Even though the new study suggests these issues might not arise for drivers using CBD oil, the study team cautions that their findings apply only to the specific doses they tested. At higher doses of CBD, or combined with other substances, it’s possible drivers might not perform optimally.
“This study looked at CBD in isolation only,” Dr. McCartney said. “Drivers taking CBD with other medications should do so with care.”