Citation: Sekula, A.D.; Puspanathan, P.; Downey, L.; Liknaitzky, P. Producing Altered States of Consciousness, Reducing Substance Misuse: A Review of Psychedelic- Assisted Psychotherapy, Transcendental Meditation and Hypnotherapy. Psychoactives 2024, 3, 137–166. https://doi.org/ 10.3390/psychoactives3020010 Academic Editor: Ricardo Dinis-Oliveira Received: 9 August 2023 Revised: 23 February 2024 Accepted: 7 March 2024 Published: 25 March 2024 Copyright: © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Review Producing Altered States of Consciousness, Reducing Substance Misuse: A Review of Psychedelic-Assisted Psychotherapy, Transcendental Meditation and Hypnotherapy Agnieszka D. Sekula 1,2, *, Prashanth Puspanathan 2 , Luke Downey 1 and Paul Liknaitzky 3,4 1 Centre for Human Psychopharmacology, Swinburne University of Technology, Hawthorn 3122, Australia 2 Enosis Therapeutics, 2 Gwynne Street, Melbourne 3121, Australia; prash@enosistherapeutics.com 3 Department of Psychiatry, School of Clinical Sciences, Monash University, Melbourne 3168, Australia 4 Turner Institute, School of Psychological Sciences, Monash University, Melbourne 3168, Australia * Correspondence: agnieszka@enosistherapeutics.com Abstract: A set of interventions that can produce altered states of consciousness (ASC) have shown utility in the treatment of substance misuse. In this review, we examine addiction-related outcomes associated with three common interventions that produce ASCs: psychedelic-assisted psychotherapy (PP), Transcendental Meditation (TM) and hypnotherapy (HT). While procedurally distinct, all three interventions are associated with some common phenomenological, psychological, and neurobiologi- cal features, indicating some possible convergent mechanisms of action. Along with addiction and mental health outcomes, these common features are reviewed, and their impact on substance misuse is discussed. While our review highlights some mixed findings and methodological issues, results indicate that PP and TM are associated with significant improvements in substance misuse, alongside improvements in emotional, cognitive and social functioning, behavior-change motivation, sense of self-identity, and meaning. In contrast, and despite its broader acceptance, HT has been associated with mixed and minimal results with respect to substance misuse treatment. Authors identify key research gaps in the role of ASC interventions in addiction and outline a set of promising future research directions. Keywords: substance misuse; addiction; psychedelics; transcendental meditation; hypnosis; hypnotherapy; review; altered states of consciousness; psilocybin; LSD; ibogaine; ketamine; meditation; trance 1. Introduction Addiction is defined as a chronic, compulsive need to engage in a behavior despite its harmful effects and/or the individual’s wish to stop [1]. The prevailing mechanistic understanding is of a complex interplay of biological, psychological, and social factors, and available treatments target one or a combination of these determinants. A number of treatment modalities that entail the production of an Altered State of Consciousness (ASC) have shown promise in treating various substance use disorders [2,3], yet the nature and strength of the evidence remain unclear. This review explores treatment outcomes associated with substance misuse interventions that produce ASCs and describes alterations in key biopsychosocial measures relevant to addiction. While definitions of ASCs vary and are frequently imprecise, we can arrive at a useful operationalization through “change in the overall pattern of subjective experience” [4], a “qualitative... not just quantitative shift” [5], and a “sufficient deviation” [6] within a wide range of mental functions [4], and crucially within “Primary Consciousness” [7]. That is, ASCs are a noticeable (often dramatic) and qualitative alteration to the fundamental “fabric of awareness”, typically accompanied by alterations to perception, cognition, and affect. The intentional induction of ASCs through a range of methods is commonplace throughout Psychoactives 2024, 3, 137–166. https://doi.org/10.3390/psychoactives3020010 https://www.mdpi.com/journal/psychoactives