Synthetic delta-9-tetrahydrocannabinol elicits schizophrenia-like negative symptoms which are distinct from sedation.
It is unknown if cannabis recreates the negative symptoms of schizophrenia. Healthy male volunteers (n 22) completed two experimental sessions in which they received intravenous (IV) delta-9-tetrahydrocannabinol (THC) 2.5 mg or placebo in a randomised counterbalanced order. Negative symptoms were rated using the self-reported community assessment of psychic experiences scale (CAPE). Sedation was rated using the mood-adjective check-list (UMACL). Plasma concentrations of THC were measured over the course of the study. Data were analysed by non-parametric tests. Participants reported an increase in negative symptoms from baseline under THC but not placebo conditions (p < 0.001). Negative symptoms showed no relationship with self-rated sedation or plasma concentrations of THC. At plasma concentrations resembling recreational use, THC elicited schizophrenia-like negative symptoms which were not merely attributable to sedation. In the community, negative symptoms may be an adverse effect of cannabis use.