Bern, Switzerland: The inhalation of CBD-dominant cannabis flowers does not influence subjects’ reaction time, concentration, balance, time perception, or other skills associated with driving ability, according to data published in the journal Forensic Sciences Research. 

A team of Swiss researchers assessed the influence of either CBD-dominant cannabis (16.6 percent CBD and 0.9 percent THC) or placebo on a variety of neurocognitive and psychomotor skills. Researchers observed “no symptoms of impairment” and “no significant impact on driving ability” in study subjects who inhaled CBD-dominant cigarettes.

Despite showing no impairment of performance, several subjects did nonetheless test positive for trace levels of THC in their blood 45 minutes after smoking. Authors cautioned that subjects’ elevated THC levels would place them in violation of certain traffic safety per se laws that criminalize the operation of a motor vehicle with detectable quantities of THC or THC metabolites in the driver’s bloodstream. 

Numerous studies have confirmed that the presence of THC in blood is not predictive of psychomotor impairment. As a result, NORML opposes the imposition of THC per se thresholds for cannabinoids in traffic safety legislation, opining: “The sole presence of THC and/or its metabolites in blood, particularly at low levels, is an inconsistent and largely inappropriate indicator of psychomotor impairment in cannabis consuming subjects. … Lawmakers would be advised to consider alternative legislative approaches to address concerns over DUI cannabis behavior that do not rely solely on the presence of THC or its metabolites in blood or urine as determinants of guilt in a court of law. Otherwise, the imposition of traffic safety laws may inadvertently become a criminal mechanism for law enforcement and prosecutors to punish those who have engaged in legally protected behavior and who have not posed any actionable traffic safety threat.”

Full text of the study, “Impact of smoking cannabidiol (CBD)-rich marijuana on driving ability,” appears in Forensic Sciences Research. Additional information is available from the NORML fact sheet, “Marijuana and Psychomotor Performance.” NORML’s white paper addressing per se limits is available online.