New research from the University of Sydney has found that even 1500mg, the highest daily medicinal dose of cannabidiol (CBD), has no impact on driving or drivers’ cognitive abilities.
The study published in the Journal of Psychopharmacology observed 17 participants undertaking simulated driving tasks after consuming either a placebo or 15, 300, or 1500 mg of CBD in oil.
This is the first study that involved testing CBD oil in drivers two years after a study from the Lambert Initiative for Cannabinoid Therapeutics at the University of Sydney, conducted at Maastricht University in the Netherlands, established that vaping CBD does not affect driving performance.
Frequently consumed dosages are safe
The participants in the newest study were healthy individuals 18 to 65 years old, holding an unrestricted driving license for more than a year, and who had not used cannabis in more than three months. The amounts administrated to the participants in this study represent frequently consumed dosages – up to 150mg/day over the counter; and up to 1500mg/day for conditions like epilepsy, pain, sleep disorders, and anxiety. The formulation used was synthetic CBD (100 mg/mL) in medium-chain triglyceride (MCT) oil, and the placebo consisted of MCT oil only.
The scientists measured driving performance at 45–75 and 210–240 min post-treatment using a fixed-base driving simulator equipped with standard vehicle controls and a custom-built scenario that has previously demonstrated sensitivity to the effects of Δ9-THC.
They selected the timing of the second drive to coincide with peak plasma CBD concentrations reported at ~3 h after consuming 25 or 300 mg CBD and ~4 h after consuming 1500 mg CBD. The driving test incorporated two activities: a seven-minute ‘car following’, during which participants maintained what they considered a ‘safe distance’ between themselves and a lead vehicle accelerating and decelerating (90–110 km/h) at 30 s intervals, and a ~25-min ‘standard’ component along a highway and rural roads with posted speed limits of 110 and between 60–100 km/h, respectively. The Simulator’s software program automatically recorded data, and the participants were instructed to follow all road rules and drive in the center of their lane.
Cognitive function was assessed at Baseline, Pre-Drive 1, and Pre-Drive 2 using three computerized tasks that have previously demonstrated sensitivity to the effects of Δ9-THC. Subjective feelings, namely ‘stoned’, ‘sedated’, ‘alert’, ‘anxious’ and ‘sleepy’, were measured at all time points using 100 mm visual analog scales (VAS), where 0 represented ‘not at all’ and 100 represented ‘extremely’. State anxiety was also measured at these times using the 6-item Short Form State and Trait Anxiety Inventory (STAI-S).
As a result, the scientists concluded that no dose of CBD induced feelings of intoxication or appeared to impair either driving or cognitive performance.
“Though CBD is generally considered ‘non-intoxicating’, its effects on safety-sensitive tasks are still being established,” said lead author Dr. Danielle McCartney, from the University’s Lambert Initiative for Cannabinoid Therapeutics. “Our study is the first to confirm that, when consumed on its own, CBD is driver-safe.”
“We do, however, caution that this study looked at CBD in isolation only and that drivers taking CBD with other medications should do so with care,” Dr. McCartney said.
Most countries, including Australia, allow people to drive after consuming CBD. In New South Wales, it is legal provided a driver is not ‘impaired’ due to fatigue and/or lower blood pressure. Recent University of Sydney research shows that around 55,000 requests to access medicinal CBD have been approved in Australia since 2016, most commonly prescribed for pain, sleep disorders, and anxiety.