The United Nations this week reclassified cannabis by removing it from the category of most dangerous and addictive drugs, which includes heroin.
Meanwhile, a landmark study was published on cannabis and driving ability, which showed that cannabidiol (CBD), a cannabis component now widely used for medical purposes, does not impair driving.
“These findings indicate for the first time that CBD, when given without THC, does not affect a subject’s ability to drive,” said lead author Dr Thomas Arkell. “That’s great news for those using or considering treatment using CBD-based products.”
Led by the Lambert Initiative for Cannabinoid Therapeutics at the University of Sydney and conducted at Maastricht University in the Netherlands, the study’s results were published this week in the Journal of the American Medical Association.
There has been substantial growth in medical treatment using cannabis-related products in Australia and overseas. This includes increasing use of CBD-containing products for conditions such as epilepsy, anxiety, chronic pain and addictions. Many currently available products also contain a mixture of THC and CBD.
The research also measured the effects of driving with THC in one’s bloodstream—the intoxicating cannabis component tetrahydrocannabinol—and found that moderate amounts produced mild driving impairment that lasted up to four hours.
Participants inhaled vaporized cannabis containing various mixes of THC and CBD, or a placebo cannabis, then went for a 60-mile drive (100-km) under controlled conditions on public highways both 40 minutes and four hours later. Cannabis containing mainly CBD did not impair driving while cannabis containing THC, or a THC/CBD mixture, caused mild impairment measured at 40 minutes later but not after four hours.
“With cannabis laws changing globally, jurisdictions are grappling with the issue of cannabis-impaired driving. These results provide much needed insights (that) can help to guide road-safety policy,” said Dr Arkell. “These results should allow for evidence-based laws and regulation for people receiving medical cannabis.”
“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 Lambert Initiative Director, Professor Iain McGregor.
METHOD
The one-hour driving test was conducted on a public highway in a dual control car with driving instructor, using a well-established scientific test that measures standard deviation of vehicle position (SDLP), including lane weaving, swerving, and overcorrecting.
The amount of THC vaporized by participants was enough to cause strong feelings of intoxication.
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, said authors of the study on JAMA.
“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.”
