Dope findings: THC produces only ‘mild driving impairment’
CANNABIS component cannabidiol (CBD) does not impair driving, and tetrahydrocannabinol (THC) produces mild driving impairment lasting up to four hours, according to a new study by the University of Sydney.
Lead author Dr Thomas Arkell confirmed the findings.
“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,” he said.
The study was led the Lambert Initiative for Cannabinoid Therapeutics at the University of Sydney and conducted at Maastricht University in the Netherlands.
It was published last week in the prestigious Journal of the American Medical Association.
The research involved people inhaling vaporised cannabis containing different mixes of THC and CBD, then going for a 100-kilometre drive 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, Dr Arkell said.
“With cannabis laws changing globally, jurisdictions are grappling with the issue of cannabis-impaired driving. 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.
“Road safety is a primary concern,” Dr Arkell said.
“These results should allow for evidence-based laws and regulation for people receiving medical cannabis.”
The study involved giving 26 healthy participants four different types of cannabis in a random order to vaporise on four separate occasions.
Each participant’s driving performance was then assessed on the road in real-world conditions along a 100-kilometre stretch of public highway in a dual control car with a driving instructor present.
The tests were done at Maastricht University in the Netherlands using a well-established scientific test that measures standard deviation of vehicle position (SDLP), an index of lane weaving, swerving and overcorrecting.
Participants vaporised cannabis containing mainly THC, mainly CBD, THC and CBD in combination, or placebo cannabis (no active components).
The amount of THC vaporised by participants was enough to cause strong feelings of intoxication.