Ketamine, a drug that blocks NMDA glutamate receptors, produces symptoms resembling schizophrenia. Analyzing the Positive and Negative Syndrome Scale (PANSS) in four groups—135 healthy people given ketamine or saline, 187 chronic ketamine abusers, 154 early-course schizophrenia patients, and 522 chronic schizophrenia patients—revealed five similar symptom dimensions (positive, negative, cognitive, depressed, excitement/dissociation) across all groups. The chronic ketamine group's symptom structure more closely matched the schizophrenia groups than the acute ketamine group did. Symptoms were milder in ketamine users than in schizophrenia patients (Cohen's d = 0.7). The findings suggest ketamine-induced psychosis shares symptom dimensions with schizophrenia, though confounding factors warrant caution.
Psilocybin, a hallucinogen that models acute psychosis, alters brain connectivity in ways similar to psychotic disorders. In a double-blind placebo-controlled trial with 20 healthy subjects, standard coherence analysis showed decreased connectivity in theta, alpha, and beta bands, especially in frontotemporal and frontoparietal regions and between frontal hemispheres. Higher frequencies showed less significant changes, often in the opposite direction. Lagged coherence analysis revealed increased connectivity in high gamma (50-100 Hz) but no changes in lower frequencies. These preliminary findings suggest psilocybin induces brain connectivity changes characteristic of psychosis, supporting its use as a model for studying psychotic symptoms.