Both THC-dominant and THC/CBD equivalent cannabis increased lane weaving during simulated driving but had little effect on other driving measures. Impairment on the Digit Symbol Substitution Task, Divided Attention Task, and Paced Auditory Serial Addition Task occurred with both active cannabis types, with worse performance on the latter two tasks after THC/CBD equivalent cannabis. Subjective feelings of being "stoned" and confidence in driving ability did not differ by CBD content. Peak plasma THC concentrations were higher after THC/CBD equivalent cannabis, suggesting a possible pharmacokinetic interaction. Cannabis with equivalent CBD and THC appears no less impairing than THC-dominant cannabis, and CBD may exacerbate THC-induced impairment in some circumstances.
A healthy 30-year-old man experienced auditory and visual hallucinations after inhaling vaporized cannabis containing 25 mg of THC in a controlled laboratory study. His scores on the Hallucinogen Rating Scale (HRS) were higher on the Volition, Intensity, Perception, and Somaesthesia subscales compared to maximum doses of cannabis, psilocybin, dextromethorphan, or salvinorin A from other studies. However, his Affect and Cognition subscale scores were lower than those for psilocybin and dextromethorphan, indicating the hallucinatory experience was qualitatively different from classic hallucinogens. The authors suggest cannabis-induced hallucinations may involve a unique pharmacological mechanism and should be considered as a potential adverse event in clinical cannabis use.