World-first cannabis study finds CBD alone doesn't impair driving ability

A novel study investigating the effects of cannabis on driving in a real-world context has found cannabidiol (CBD) alone does not impair driving ability. The landmark finding promises to be invaluable in guiding road safety regulations as cannabis laws shift across the globe.

“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,” explains Iain McGregor, from the University of Sydney and an author on the new 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.”

There are more than 100 different cannabinoids in cannabis. CBD and tetrahydrocannabinol (THC) are the two most prominent chemicals, and THC is primarily associated with the plant’s psychoactive euphoric effects. Meanwhile, CBD is increasingly being found to confer a number of positive health outcomes. It recently became the first cannabis-derived compound ever approved by the FDA, to reduce seizures in severe forms of epilepsy.

This new study, a collaboration between Australian and Dutch researchers, is the first to focus specifically on the effect of CBD alone, or in combination with THC, on driving ability in real-world conditions.

The novel experiment recruited 26 subjects whose driving performance was tested on four occasions after vaporizing either THC alone, CBD alone, a THC/CBD combination, or a placebo.

The test involved driving on a real highway under controlled conditions for one hour on two occasions, 40 minutes after vaporizing the drug and again four hours later. Impairment was assessed using a measure called the standard deviation of vehicle position (SDLP), which tracks how much a person drifts or weaves within a given lane, and has been used in the past to establish impairment levels for drugs such as alcohol and Valium.

Compared to placebo the researchers found no driving impairment differences 40 minutes after vaporizing just the CBD. This compares to a mild impairment detected in both THC and THC/CBD tests after 40 minutes.

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

Another important finding from the study was a lack of impairment detected in any of the four groups in the driving test conducted four hours after drug administration. Prior research has found cannabis can generate mild driving impairments up to three hours after consumption. These temporary impairments generally diminish around four hours after consumption and these findings affirm those previous studies.

This is a relatively crucial finding as roadside testing for cannabis intoxication is still a controversial topic. Scientists are yet to produce a reliable commercial device to objectively measure cannabis intoxication and THC metabolites can be detected for days, or even weeks, after consumption.

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

The new study was published in the journal JAMA.

Source: University of Sydney