The phenomenology of acute THC-psychosis
P. Morrison, S. Kapur, R. Murray
European Psychiatry January 1, 2009 Peer reviewed DOI: 10.1016/s0924-9338(09)70379-7
Summary
Synthetic intravenous THC significantly increased both self-rated and observer-rated positive psychotic symptoms in healthy subjects, with a correlation of r=0.62. Participants also experienced heightened negative symptoms and marked impairments in working memory and executive functioning. This study provides evidence that THC can induce acute psychotic reactions similar to those seen in schizophrenia, affecting multiple symptom dimensions without causing sedation. Additionally, preliminary findings suggest that cannabidiol may inhibit some of these THC-elicited positive symptoms.
Study at a glance
| Design | randomized controlled trial |
|---|---|
| Sample size | 22 |
| Population | healthy subjects |
| Key finding | THC significantly increased positive psychotic symptoms, negative symptomatology, and impaired cognitive functioning in healthy participants. |
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.