A study in Switzerland shows smoking CBD-rich cannabis – even if participants exceeded the legal THC limit – has no impact on driving ability or vital signs. The study’s authors wanted to investigate their effect on driving safety because recently, the Swiss CBD market has become so popular.
Thirty-three participants – 19 men and 14 women between the ages of 19 and 31 – were handed a joint paper filled with CBD-rich marijuana or a placebo. The placebo contained Knaster Hemp, a nicotine-free and cannabinoid-free herbal mixture with a hemp aroma. Researchers then issued multiple typical DUI tests. Participants were tested a second time between seven and 14 days later, and the CBD and placebo groups were reversed. The analysis distinguished three groups: CBD versus placebo consumption, women versus men, and the first trial versus the second trial.
To confirm participants were above the legal THC limit for driving, researchers took participants’ blood samples after smoking and after completion of their research to determine the cannabinoid concentrations of CBD, THC, and THC-metabolites.
The study found no significant differences in reaction time or motor time between smoking CBD-rich marijuana and placebo. Interestingly, there was a difference in reaction time between men and women after consuming CBD-rich marijuana.
The Cognitrone test asks participants to compare one geometric figure with four other geometric figures. No significant differences were observed in the analysis of that test between; those smoking CBD-rich marijuana and placebo, nor any significant differences between men and women or between the first and second trials.
There were three standard tests used regularly by trained medical personnel to determine neurological deficits after substance misuse were given to participants for balance and coordination.
In order to test their balance and internal clock, participants were asked to stand with eyes closed and arms out. They were instructed to open their eyes after they believed 30 seconds had passed. The results were within the normal range of 20 to 45 seconds. Both the CBD and placebo groups were able to maintain “a secure balance.”
In the standard finger-to-nose test, 32 of the 33 participants touched the tip of the nose with each action,” regardless of whether the CBD or placebo joint was smoked. After consuming the CBD joint, only one participant “missed the tip of his/her nose twice.”
During the walk-and-turn test, everyone walked without interruption, “and no participants missed the heel-to-toe or hop around, regardless of whether they smoked the CBD or placebo joint.” The only discrepancies were with 19 of the 66 tests taking the wrong number of steps, especially during the turn. Still, those errors were evenly spread over both groups: 10 times after a participant smoked the CBD joint and nine times after consuming the placebo joint.
Blood tests revealed that all participants had a blood THC level above the legal limit when the testing began. But, in those tested, researchers observed no significant differences in behavior, blood pressure, language, mood, orientation, and psychomotor skills.
Despite THC concentrations reaching levels typically considered to cause symptoms of impairment in other studies in which THC-rich marijuana was smoked, researchers observed no signs of impairment in the current study,” the authors wrote.
The conclusions from the Swiss study are similar to studies at the University of Sydney about CBD’s impact on driving. Concluding that a “per se limit” on THC concentration in the blood doesn’t accurately predict impairment in drivers, Michigan’s Impaired Driving Safety Commission “recommends the use of a roadside sobriety test(s) to determine whether a driver is impaired.”
A 2019 study concluded that those who drive at the legal THC limit weren’t statistically likelier to be involved in an accident than individuals who haven’t used marijuana.
In 2019, the Congressional Research Service determined that “marijuana consumption can affect a person’s response times and motor performance… studies of the impact of marijuana consumption on a driver’s risk of being involved in a crash have produced conflicting results, with some studies finding little or no increased risk of a crash from marijuana usage.”