Pattern Breaking: A Complex Systems Approach to Psychedelic Medicine

This theory-building article (2022) further refines the REBUS model, using complex systems theory (CST) to propose that psychedelics act as destabilisers of stuck patterns of thinking (‘attractors’ or ‘overweighted priors’) which could explain both the acute (peak) and subsequent period in which psychedelics can help one get ‘unstuck’.


“There is growing evidence for the safety and efficacy of psychedelic therapy in mental health care. What is less understood however, is how psychedelics act to yield therapeutic results. In this paper we propose that psychedelics act as destabilisers — both in a psychological and a neurophysiological sense. Our proposed framework builds on the ‘entropic brain’ hypothesis, according to which psychedelics increase the entropy of spontaneous cortical activity and, in parallel, the richness or depth of content of psychological experience. The so-called ‘RElaxed Beliefs Under pSychedelics’ (REBUS) model is a predictive-coding inspired extension to this hypothesis, which states that psychedelics’ entropic action is paralleled by a relaxation of prior assumptions. Here we adopt a complex systems theory (CST) perspective, proposing that psychedelics act as destabilisers of excessively reinforced fixed points — or ‘attractors’ — which translates as the breaking of excessively reinforced or overweighted patterns of thinking or behaving. Our CST approach explains how psychedelic-induced increases in brain entropy destabilise neurophysiological set-points that are synonymous with overweighted priors, thereby augmenting and enriching the account given by REBUS. We believe that this perspective helps inspire conceptualisations of psychedelic psychotherapy — bearing relevance both to the peak psychedelic experience and subsequent sub-acute period of potential recovery. We discuss implications for risk mitigation and treatment optimization in psychedelic medicine.”

Authors: ‪Inês Hipólito, ‬Jonas Mago, Fernando E. Rosas & Robin L. Carhart-Harris

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Pattern Breaking: A Complex Systems Approach to Psychedelic Medicine

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Published in
July 13, 2022
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Authors associated with this publication with profiles on Blossom

Fernando Rosas
Dr. Fernando E. Rosas is a Postdoctoral Researcher at Imperial College London, based at the Centre For Psychedelic Research.

Robin Carhart-Harris
Dr. Robin Carhart-Harris is the Founding Director of the Neuroscape Psychedelics Division at UCSF. Previously he led the Psychedelic group at Imperial College London.

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REBUS and the Anarchic Brain: Toward a Unified Model of the Brain Action of Psychedelics
The REBUS and the anarchic brain argues that psychedelics work to relax the precision of high-level priors or beliefs, thereby liberating bottom-up information flow, particularly via intrinsic sources such as the limbic system.

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