The phenomenology of acute THC-psychosis

Intravenous delta-9-tetrahydrocannabinol (THC) can produce a temporary psychotic reaction in healthy people. In a double-blind, placebo-controlled experiment with 22 participants, a single 2.5 mg dose of THC significantly increased both self-reported and observer-rated positive psychotic symptoms, which were closely linked (correlation of 0.62). The symptoms involved a disrupted sense of self-agency and heightened paranoia. Participants also reported more negative symptoms, which were not due to sedation, and their working memory and executive function were consistently impaired. The findings suggest THC recreates symptoms across three major dimensions of schizophrenia without clouding consciousness. Preliminary evidence indicates that cannabidiol (CBD) may inhibit THC-induced positive symptoms.

Study at a glance

Abstract

It has long been known that cannabis can elicit an acute psychotic reaction. Recent work shows that, of the 60 cannabinoid molecules in the plant, delta-9-tetrahydrocannibinol is responsible for the central effects of cannabis. Here we aimed to investigate, in more detail, the psychological effects of synthetic intravenous THC in healthy subjects. Over 2 experimental sessions, participants (N=22) were administered 2.5mg IV THC or placebo under randomised, double-blind conditions. Psychological reactions were assessed using standard rating instruments and a battery of cognitive tests was completed.Following THC, there was a significant increase in self-rated and observer-rated positive psychotic symptoms which were highly correlated (r=0.62, p=0.001).Phenomena centered on de-synchronisation of self-agency (ipseity disturbance) and hypersalience/paranoia. Participants also reported a significant increase in negative symptomatology under THC conditions, which was not explained by sedation. Finally, working memory/executive functioning was markedly and consistently impaired by THC.Here we provide further evidence that THC can elicit an acute psychotic reaction in a proportion of healthy subjects. Acute THC-psychosis elicits positive, negative and cognitive symptoms. Compared with other drug models THC recreates symptomatology across 3 major dimensions of schizophrenic psychosis without sedation/clouding of consciousness. Here we also present preliminary evidence that the molecule cannabidiol (CBD) inhibits THC-elicited positive symptoms. Current work in our laboratory is exploring the underlying mechanisms.