Hallucinations Under Psychedelics and in the Schizophrenia Spectrum

An Interdisciplinary and Multiscale Comparison

Pantelis Leptourgos; Martin Fortier-Davy; Robin Carhart-Harris; Philip R. Corlett; David Dupuis; Adam L. Halberstadt; Michael Kometer; Eva Kozakova; Frank LarØi; Tehseen N. Noorani; Katrin H. Preller; Flavie Waters; Yuliya Zaytseva; Renaud Jardri


Schizophr Bull. 2020;46(6):1396-1408. 

In This Article


In this article, we sought to compare and contrast hallucinations in SCZs and under psychedelics. We identified several interesting common features: both experiences are related to a reduced integration and stability of functional networks, as well as a distorted anti-correlation between resting-state and task-positive networks. Furthermore, both experiences are afforded a strong metaphysical meaning. We also highlighted various crucial differences: First, psychedelics over-engage primary sensory cortices, hallucinations in SCZs, on the other hand, are mostly related to overactivation of associative networks. Furthermore, while drug-induced psychosis mostly encompasses VH (often geometric) with preserved insight, SCZs is characterized by AH (mostly voices) and poor reality monitoring. Additionally, we pointed out a number of topics that need further investigation, more particularly the role of serotonin in SCZs, the prevalence of MMH in both experiences and the potential cultural impact on hallucinations in SCZs. Finally, we suggested that psychotic experiences, regardless of their diagnostic categorization, might be underlain by the same computational mechanisms that tie together subjectivity and neural implementation, namely altered predictive processing. Future studies will have to clarify whether the same (eg, strong priors) or different (eg, climbing vs descending loops) impairments underscore these different psychotic experiences.