A high dose of delta9-tetrahydrocannabinol, the main psychoactive component of cannabis, induces anxiety and psychotic-like symptoms in healthy volunteers, and these effects are significantly reduced by cannabidiol (CBD), a cannabis constituent without typical cannabis effects. Studies in animal models and healthy volunteers suggest an anxiolytic-like effect of CBD. Its antipsychotic-like properties have been investigated in animal models and supported by studies on healthy volunteers using binocular depth inversion and ketamine-induced psychotic symptoms. Open case reports and a preliminary controlled clinical trial indicate that CBD may be a safe, well-tolerated alternative treatment for schizophrenia. Future studies in other psychotic conditions are indicated.
Delta9-tetrahydrocannabinol (THC), a psychoactive constituent of cannabis, increased psychotic symptoms, anxiety, intoxication, and sedation in healthy men with minimal prior cannabis use, while cannabidiol had no significant effect on these measures. Verbal learning performance was not significantly affected by either drug. THC altered brain activation in the parahippocampal gyrus during encoding and in the ventrostriatum during retrieval, with the ventrostriatal change directly correlating with induced psychotic symptoms. These findings suggest THC modulates mediotemporal and ventrostriatal function, potentially underlying cannabis's effects on verbal learning and psychosis.