Cannabis use affects cognition differently in schizophrenia patients versus healthy individuals. Healthy subjects who started cannabis early and used high-potency cannabis longer showed poorer working memory and attention. In schizophrenia patients, cannabis use is linked to worsened symptoms, longer and more frequent psychotic episodes, and poorer treatment outcomes. However, patients with schizophrenia who use cannabis have better overall cognitive performance than non-using patients.
Delta-9-Tetrahydrocannabivarin (THCV), a natural cannabinoid similar to THC, can both mimic and block some of THC's effects depending on dose. In a study with 16 male rats trained to distinguish THC from a placebo, THCV partially substituted for THC at 3 mg/kg (54.6% of responses), but at 6 mg/kg it reversed the effects of a low THC dose. THCV did not alter blood levels of THC or its metabolite 11-OH-THC. The results suggest THCV acts as a partial CB1 receptor agonist, producing a mix of agonist and antagonist effects.