A small, randomized clinical trial has found that vaporized cannabis that is high in cannabidiol (CBD) and low in tetrahydrocannabinol (THC) does not lead to driving impairment. They also found that the intoxicating effects of THC, as measured by driving impairment, cannot be offset by comparable levels of CBD. Products that contain equal parts THC and CBD cause impairment just like products that are THC dominant.
While driving under the influence of THC, the active ingredient in cannabis that produces the feeling of being “high,” has long been associated with increased crash risk and is consequently illegal, questions have persisted about how CBD effects drivers. Though CBD is non-intoxicating, it still does have psychotropic effects.
Anecdotal evidence has long suggested that these effects do not impact an individual’s ability to drive and that there is no link of CBD use and an increased risk of being in a car accident. Conversely, the U.S. Food and Drug Administration notes that Epidiolex®, an FDA approved formulation of CBD, can cause somnolence and sedation, and that clinicians should “advise patients not to drive or operate machinery until they have gained sufficient experience” on the drug.
While it is still strongly recommended that clinicians should advise patients to exercise caution as they learn how CBD effects them personally, a new paper published in JAMA by a team of researchers in Australia led by Thomas Arkwell of the University of Sydney found that moderate doses of CBD are not associated with driving impairment. The standard deviation of lateral position (which is a measure that includes lane weaving, swerving, and overcorrecting) was no different among those who were given CBD and those who were given placebo.
These findings do have caveats. The authors note that "the effect size for CBD-dominant cannabis may not have excluded clinically important impairment, and the doses tested may not represent common usage.” Two additional limitations include the size of the study (N = 26) and its inclusion of only healthy individuals between the ages of 20 and 50 who were at least somewhat acclimated to the effects of cannabis.
The whole study can be found here.