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.

Department of Anthropology University of Durham Durham UK

Department of Applied Neurosciences and Brain Imaging National Institute of Mental Health Klecany Czechia

Department of Biological and Medical Psychology Faculty of Psychology University of Bergen Bergen Norway

Department of Psychiatry and Medical Psychology 3rd Faculty of Medicine Charles University Prague Prague Czechia

Department of Psychiatry Connecticut Mental Health Center Yale University New Haven CT

Department of Psychiatry University of California San Diego La Jolla CA

Department of Psychology Faculty of Arts Charles University Prague Czechia

Imperial College London London UK

Institut Jean Nicod École des Hautes Études en Sciences Sociales École Normale Supérieure PSL Research University Paris France

Laboratoire de Neurosciences Cognitives et Computationnelles ENS INSERM U960 PSL Research University Paris France

Norwegian Center of Excellence for Mental Disorders Research University of Oslo Oslo Norway

Pharmaco Neuroimaging and Cognitive Emotional Processing Department of Psychiatry Psychotherapy and Psychosomatics Psychiatric University Hospital Zurich University of Zurich Zurich Switzerland

Psychology and Neuroscience of Cognition Research Unit University of Liège Liège Belgium

Research Service VA San Diego Healthcare System San Diego CA

School of Psychological Sciences The University of Western Australia Perth Western Australia

Univ Lille INSERM U1172 CHU Lille Lille Neuroscience and Cognition Centre Plasticity and SubjectivitY team Lille France

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