The mechanisms of psychedelic therapy

‘The mechanisms of psychedelic therapy’ presents arguments against three theories of psychedelic therapy. The Molecular Neuroplasticity Theory ascribes therapeutic benefits to an experience-independent molecular mechanism. This theory is undermined by the correlation between ‘mystical-type experiences’ and beneficial outcomes, which suggests that genuinely psychological mechanisms are involved. The Metaphysical Belief Theory and the Metaphysical Alief Theory fare better on this count: both ascribe beneficial outcomes to the transcendent vision of a ‘Joyous Cosmology’ supposedly encountered in the mystical-type experience. However, these theories struggle to account for the fact that some patients satisfy psychometric criteria for a mystical-type experience without undergoing a non-naturalistic metaphysical hallucination. The psychometric criteria can also be satisfied by more naturalistic experiences of ego dissolution and connectedness. The conclusion is that psychedelics cause lasting benefits via some genuinely psychological factor that (i) correlates with the construct of a mystical-type experience, but (ii) is independent of non-naturalistic metaphysical ideations.

The phenomenology of psychedelic therapy

‘The phenomenology of psychedelic therapy’ provides a selective overview of experiences commonly reported by those who take psychedelics in controlled and structured settings, such as clinical trials and religious rituals. The first half of this chapter reviews a variety of typical changes to perception and the sense of self. The second half reviews qualitative evidence concerning patients’ impressions of the therapeutic process. Patients who receive psychedelics in clinical trials sometimes, but not always, describe non-naturalistic metaphysical epiphanies concerning the existence of a cosmic consciousness, spirit world, or divine Reality. More commonly emphasised are experiences of psychological insight, beneficial changes to self-representation, intense and cathartic emotional experiences, and feelings of connectedness and acceptance. This evidence provides initial clues that psychedelics’ therapeutic effects may not be due entirely to the induction of non-naturalistic metaphysical ideations.

Epistemology

‘Epistemology’ argues that controlled psychedelic administration can have significant epistemic benefits consistent with a naturalistic worldview. The most obvious candidate for propositional knowledge, or knowledge that, is psychodynamic insight into one’s previously unknown mental states. This chapter argues that such insights are probably often accurate, but cannot be trusted uncritically: sober scrutiny is essential. It further argues that psychedelics offer knowledge by acquaintance with various aspects of the human mind, including its potential for diverse and beneficial modes of attention and cognition. At later times, subjects can re-evoke these beneficial modes. Therefore, psychedelics also make available ability knowledge, or knowledge how. The chapter argues that psychedelic experiences also facilitate the acquisition of new knowledge of old facts, allowing subjects to experience existing beliefs in more vivid and motivating ways. Finally, the chapter argues that psychedelic experiences can cause epistemic benefits indirectly, via their psychological benefits. In Lisa Bortolotti’s terminology, therapeutic psychedelic experiences are epistemically innocent.

On the need for a natural philosophy of psychedelics

‘On the need for a natural philosophy of psychedelics’ provides a brief overview of the history of psychedelics in science and psychiatry, and a detailed review of recent evidence for their therapeutic and transformative efficacy. The chapter reviews clinical trials showing that one or two controlled psychedelic experiences can durably reduce symptoms of anxiety, depression, and addiction, and can cause lasting psychological benefits in healthy subjects. The chapter also reviews evidence that these beneficial effects are mediated by the occurrence of ‘mystical-type’ experiences. This evidence gives rise to the Comforting Delusion Objection that is the central focus of the book. Existing responses involve (i) rejecting philosophical naturalism, or (ii) downplaying the importance of epistemic factors in the evaluation of psychiatric treatments. The chapter raises problems for both approaches, and outlines a new one: to show that the Objection fails even if naturalism is true and the epistemic status of psychedelic therapy is important.

Unbinding the self

‘Unbinding the self’ outlines the predictive self-binding account of psychedelic therapy introduced by Letheby and Gerrans (2017). On this account, the networks targeted by psychedelics integrate or ‘bind’ information from multiple sources into a hierarchical predictive model of the self. In pathological conditions, detrimental forms of self-modelling can become rigidly entrenched. By ‘unbinding’ the self-model, psychedelics facilitate experiences of ego dissolution and psychological insight in which pathological self-models can be revised. On this view, psychedelic therapy has a two-factor structure: it involves (a) the induction of neural and psychological plasticity, and (b) the discovery and consolidation of new forms of self-modelling. The chapter shows how this account can subsume many candidate mechanisms of psychedelic therapy, including feelings of connectedness and acceptance, psychological insight, emotional breakthrough, and mindfulness-related capacities. The chapter concludes with some brief remarks on philosophical questions about self and self-consciousness.

Resetting the brain

‘Resetting the brain’ examines the hypothesis that (i) large-scale neural networks become stuck in dysfunctional configurations in pathology, and (ii) psychedelics cause therapeutic benefits by disrupting these configurations, providing an opportunity to ‘reset’ the relevant networks into a healthier state. This chapter argues that this view is correct but limited; per Chapter 5, it needs to be supplemented with an account of these networks’ cognitive functions. To this end, the chapter introduces the predictive processing (PP) theory of cognition, which views the brain as an organ for prediction error minimisation. One PP-based theory of psychedelic action claims that (i) the networks targeted by psychedelics encode high-level beliefs, and (ii) psychedelic disruption of these beliefs provides an opportunity to revise them. This is the cognitive process that corresponds to the ‘resetting’ of neural networks. The chapter concludes by proposing that the beliefs most often revised in successful psychedelic therapy are self-related beliefs.

Introduction

This Introduction outlines the central focus of Philosophy of Psychedelics: the therapeutic use of psychedelics in psychiatry and its apparent conflict with philosophical naturalism. The chapter briefly describes recent findings that controlled psychedelic administration can have lasting psychological benefits for healthy subjects and for psychiatric patients. It then cites evidence that these psychological benefits are mediated by ‘mystical-type’ experiences. For those sympathetic to naturalism, the philosophical view that only the natural world exists, this prompts a concern: do psychedelics cause therapeutic benefits by inducing non-naturalistic beliefs in a cosmic consciousness or divine Reality? This Introduction outlines a plan to answer this ‘Comforting Delusion Objection’ in subsequent chapters. The basic strategy is to argue that, even if naturalism is true, psychedelic therapy is still acceptable because (i) its epistemic risks are smaller than they might appear, and (ii) it also has epistemic benefits that are consistent with naturalism.

Spirituality

‘Spirituality’ examines the import of psychedelic evidence for the philosophical project of naturalising spirituality. This chapter argues that psychedelic research vindicates the claim that there are transformative experiences and practices that can legitimately be called ‘spiritual’ and are compatible with adherence to a naturalistic worldview. The existential transformation afforded by some psychedelic experiences provides a paradigm for naturalistic spirituality: the temporary suspension of our default, self-referential mode of cognition, making available experiences of connectedness and feelings of wonder and awe. Jerome Stone (2012) has reviewed recent philosophical work on naturalistic spirituality and extracted some core ideas: notably (i) that spirituality is about connection, aspiration, and asking the Big Questions, and (ii) that these are all ways of overcoming the limitations of the ordinary sense of self. This chapter argues that psychedelic evidence supports these claims, as well as the further claim that such experiences and practices are independent of non-naturalistic metaphysical ideations.

Conclusion

The ‘Conclusion’ summarises the main ideas of Philosophy of Psychedelics and makes some suggestions for future research. The first part of the chapter provides a chapter-by-chapter summary of the arguments of the book, and lists the various testable predictions that follow from these arguments. The second part suggests some other directions for future research, pointing to outstanding questions about psychedelics in various fields of inquiry, including philosophy of science, philosophy of psychiatry, ethics, epistemology, and the philosophy of transformative experience. The third part reflects on the significance of the book’s two central theses: that the Comforting Delusion Objection to psychedelic therapy fails, and that an ‘Entheogenic Conception’ of psychedelics as agents of epistemic benefit and spiritual experience is both consistent with naturalism and plausible in light of our best current evidence.

The role of self-representation

‘The role of self-representation’ presents three lines of evidence in support of a simple hypothesis: the central mechanism of psychedelic therapy is the disruption and revision of mental representations of the self. One line of evidence connects experiences of ‘psychological insight’ to positive clinical outcomes, and the insights in question are often autobiographical in character. A second line of evidence shows that psychedelics can elevate mindfulness-related capacities for taking an open, non-reactive attentional stance toward inner experience. These capacities centrally involve changes in the sense of self. A third line of evidence links positive clinical outcomes to changes in two neural systems, the Default Mode and Salience networks. Both are implicated in self-representation by considerable independent evidence. This chapter argues that one can combine these psychological and neurobiological findings into an integrative account of psychedelic therapy by attending to the cognitive or information-processing functions of the neural systems affected by psychedelics.