In a new study, researchers examined how cannabis affects driving ability.
They found that cannabidiol (CBD), a cannabis component now widely used for medical purposes, does not impair driving.
But moderate amounts of the main intoxicating component tetrahydrocannabinol (THC) produce mild driving impairment lasting up to four hours.
These findings show the first time that CBD, when given without THC, does not affect a person’s ability to drive.
The research was conducted by a team at the University of Sydney and elsewhere.
There has been strong growth in medical treatment using cannabis-related products in Australia and overseas.
This includes increasing the 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 tested people inhaling cannabis containing different mixes of THC and CBD, then going for a 100-kilometer drive under controlled conditions on public highways both 40 minutes and four hours later.
They found 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.
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.
The team says the findings 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 the impairment.
One author of the study is Dr. Thomas Arkell.
The study is published in JAMA.
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