Disturbances of visual information processing in early states of psychosis and experimental delta-9-tetrahydrocannabinol altered states of consciousness.

In people with schizophrenia, in the prodromal phase, and in healthy volunteers given synthetic delta-9-tetrahydrocannabinol (THC), performance on a test of visual information processing (the Binocular Depth Inversion Illusion Test) was similarly impaired, and all three groups differed significantly from healthy controls who received no drug. On the Brief Psychiatric Rating Scale, the THC-treated group and the prodromal group did not differ significantly, while both differed from the schizophrenia group and from controls. The findings suggest that THC-induced altered states can model psychotic disorders, especially their prodromal states, and help explain the pro-psychotic effects of high-THC cannabis.

Study at a glance

Abstract

Recent data on alterations of the endogenous cannabinoid system in schizophrenia have raised the question of its functional role in this disease. The psychoactive compound of Cannabis sativa, delta-9-tetrahydrocannabinol (Delta9-THC), has been shown to induce psychotic symptoms, but it is unknown to what extend prodromal states of psychoses are reflected by these experimental approaches. This study compares four groups of subjects: antipsychotic-naïve patients suffering from acute paranoid schizophrenic or schizophreniform psychosis (SZ), patients in the prodromal state (IPS), healthy controls without any pharmacological intervention (HC) and a second group of healthy volunteers who were orally administered synthetic Delta9-THC (Dronabinol) (HC-THC). Neither SZ and IPS nor HC received the experimental drug. All subjects were assessed using the Brief Psychiatric Rating Scale (BPRS) and the Binocular Depth Inversion Illusion Test (BDII). The latter represents a sensitive measure of impaired visual information processing that manifests in various experimental and naturally occurring psychotic states. BDII values were well comparable in SZ, IPS and HC-THC, and all groups differed significantly to HC. The BPRS revealed no significant difference between HC-THC and IPS while both were significantly different from SZ and HC, respectively. Our results suggest that Delta9-THC-induced altered states of consciousness may serve as a useful tool for modeling psychotic disorders, particularly their prodromal states. Furthermore, they provide insight into the perceptual and psychopathological alterations induced by Delta9-THC, which is essential for the understanding of the pro-psychotic effects of herbal cannabis preparations with highly enriched Delta9-THC content.