Hallucinations Under Psychedelics and in the Schizophrenia Spectrum: An Interdisciplinary and Multiscale Comparison
This multidisciplinary review synthesises pharmacological, neuroimaging, phenomenological and anthropological evidence to show that hallucinations under psychedelics and in the schizophrenia spectrum exhibit important overlaps in mechanisms and experience but also diverge in phenomenology, neural signatures and contextual modulation. The authors integrate these multiscale findings with computational models and provide targeted recommendations for future research.
Authors
- Robin Carhart-Harris
- Katrin Preller
- Matthias Kometer
Published
Abstract
The recent renaissance of psychedelic science has reignited interest in the similarity of drug-induced experiences to those more commonly observed in psychiatric contexts such as the schizophrenia-spectrum. This report from a multidisciplinary working group of the International Consortium on Hallucinations Research (ICHR) addresses this issue, putting special emphasis on hallucinatory experiences. We review evidence collected at different scales of understanding, from pharmacology to brain-imaging, phenomenology and anthropology, highlighting similarities and differences between hallucinations under psychedelics and in the schizophrenia-spectrum disorders. Finally, we attempt to integrate these findings using computational approaches and conclude with recommendations for future research.
Research Summary of 'Hallucinations Under Psychedelics and in the Schizophrenia Spectrum: An Interdisciplinary and Multiscale Comparison'
Introduction
Hallucinations—percepts experienced without corresponding external stimulus—occur across a range of contexts, including schizophrenia-spectrum disorders (SCZs), certain neurological illnesses, the general population, and following administration of psychotomimetic drugs such as classical serotonergic psychedelics. Since the nineteenth century, researchers have debated whether drug-induced states can serve as models for psychosis. The recent resurgence of clinical and neuroscientific work on psychedelics has renewed interest in similarities and differences between pharmacologically induced experiences and those seen in SCZs. Leptourgos and colleagues, reporting from a multidisciplinary working group of the International Consortium on Hallucinations Research, set out to compare hallucinations under classical psychedelics with those observed in the schizophrenia spectrum. Their approach is explicitly multiscale: they examine synaptic pharmacology, network-level brain imaging, first-person phenomenology, anthropological evidence about cultural shaping of experiences, and computational models that might bridge these levels of analysis. The stated aim is to identify commonalities and differences and to suggest directions for future empirical work that can integrate these scales of explanation.
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Leptourgos, P., Fortier-Davy, M., Carhart-Harris, R., Corlett, P. R., Dupuis, D., Halberstadt, A. L., Kometer, M., Kozakova, E., LarØi, F., Noorani, T. N., Preller, K. H., Waters, F., Zaytseva, Y., & Jardri, R. (2020). Hallucinations Under Psychedelics and in the Schizophrenia Spectrum: An Interdisciplinary and Multiscale Comparison. Schizophrenia Bulletin, 46(6), 1396-1408. https://doi.org/10.1093/schbul/sbaa117
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