Less Vomiting With CBD Did Not Mean Protection From THC’s Cognitive Effects in Primates
Adding CBD was associated with less first-day vomiting in a small adolescent-primate experiment, but did not prevent the measured THC-related learning disruption. Improvement in one adverse outcome should not be presented as general protection.
Three small treatment groups
Twelve male squirrel monkeys received vehicle, THC alone or THC with CBD, four per group, during four months of daily treatment. The cannabinoids were injected intramuscularly. The study did not test inhaled cannabis strains or oral CBD supplements in human adolescents.
Learning and other behaviors diverged
THC initially disrupted acquisition of visual discriminations and reduced activity. With repeated treatment, group differences diminished on selected measures. Reversal-learning performance did not show a significant treatment difference, and several longer-term activity and sleep-related comparisons were also nonsignificant.
The vomiting observation was narrower
On the first dosing day, vomiting occurred in all four THC-only animals and one of four receiving THC plus CBD. That reduction was distinct from the cognitive findings: CBD did not significantly modulate the measured THC learning effects, activity changes or tolerance. The combination did not eliminate every adverse effect.
Clinical claims require matching evidence
Small groups, male-only animals, one cannabinoid combination and injected dosing constrain transfer to people. A laboratory discrimination task is also only one component of cognition. These results do not establish a protective CBD-to-THC ratio, an antidote to impairment or a treatment for human cannabis-related vomiting. They support reporting each endpoint separately, including the favorable observation and the comparisons that remained null.
Related analysis: evaluating cannabis tolerance claims.
Primary research
Withey SL; Kangas BD; Charles S; Gumbert AB; Eisold JE; George SR; Bergman J; Madras BK. Effects of daily Δ9-Tetrahydrocannabinol (THC) alone or combined with cannabidiol (CBD) on cognition-based behavior and activity in adolescent nonhuman primates. Drug and alcohol dependence (2021). DOI: 10.1016/j.drugalcdep.2021.108629.
