Studies have shown that both serotonin and glutamate receptor systems play a crucial role in the mechanisms underlying drug-induced synesthesia. The specific nature of these mechanisms, however, continues to remain elusive. Here we propose two distinct hypotheses for how synesthesia triggered by hallucinogens in the serotonin-agonist family may occur. One hypothesis is that the drug-induced destabilization of thalamic projections via GABAergic neuronal circuits from sensory areas leads to a disruption of low-level, spontaneous integration of multisensory stimuli. This sort of integration (...) regularly occurs when spatial and temporal attributes match. Destabilization of feedback loops, however, can result in incongruent experiences or binding of random thalamus activation with sensory input in a particular sensory modality. The second hypothesis builds on embodied cognition, cases in which visual images of external stimuli activate task-related neural regions. On this proposal, binding processes that do not normally generate awareness become accessible to consciousness as a result of decreased attentional discrimination among incoming stimuli. (shrink)

Recent clinical trials show that psychedelics such as LSD and psilocybin can be given safely in controlled conditions, and can cause lasting psychological benefits with one or two administrations. Supervised psychedelic sessions can reduce symptoms of anxiety, depression, and addiction, and improve well-being in healthy volunteers, for months or even years. But these benefits seem to be mediated by "mystical" experiences of cosmic consciousness, which prompts a philosophical concern: do psychedelics cause psychological benefits by inducing false or implausible beliefs (...) about the metaphysical nature of reality? This book is the first scholarly monograph in English devoted to the philosophical analysis of psychedelic drugs. Its central focus is the apparent conflict between the growing use of psychedelics in psychiatry and the philosophical worldview of naturalism. Within the book, Letheby integrates empirical evidence and philosophical considerations in the service of a simple conclusion: this "Comforting Delusion Objection" to psychedelic therapy fails. While exotic metaphysical ideas do sometimes come up, they are not, on closer inspection, the central driver of change in psychedelic therapy. Psychedelics lead to lasting benefits by altering the sense of self, and changing how people relate to their own minds and lives-not by changing their beliefs about the ultimate nature of reality. The upshot is that a traditional conception of psychedelics as agents of insight and spirituality can be reconciled with naturalism (the philosophical position that the natural world is all there is). Controlled psychedelic use can lead to genuine forms of knowledge gain and spiritual growth-even if no Cosmic Consciousness or transcendent divine Reality exists. Philosophy of Psychedelics is an indispensable guide to the literature for researchers already engaged in the field of psychedelic psychiatry, and for researchers-especially philosophers-who want to become acquainted with this increasingly topical field. (shrink)

5-MeO-DMT is a psychedelic substance with a short duration of action and intensive effects. Its therapeutic efficacy and practicality may significantly surpass those of classical psychedelics such as ayahuasca and LSD. -/- This retrospective ethnographic inquiry features a woman in her mid-thirties who witnessed her mother's violent suicide and its bloody aftermath at the age of three. Before and after that, her childhood was characterized by domestic violence and sexual abuse perpetrated by several members of her family and extended family. (...) In her twenties and thirties, she dated a member of the local mafia with the intention of asking him to kill her father, who had been the main perpetrator of the sexual abuse and violence. This plan was eventually not carried out, but it reflected her deep bitterness and wrath. -/- A process initiated in her early thirties involving four 5-MeO-DMT sessions and a few additional sessions with psilocybin and ayahuasca in the course of two years completely resolved her symptoms related to the abuses, to the extent that she could rebuild a functional relationship with her father and feel love and compassion towards him. This outcome, i.e., the complete reversal of her attitude and emotions towards her father, appeared highly unusual. For the last three years, the outcome had remained stable. -/- The article also presents the perspective of a female facilitator of this treatment process. The article contributes to a better understanding of the use of 5-MeO-DMT in severe traumatization as well as exemplifies the possible positive contributions of actors who are not medical professionals in resolving deep collective traumatization in societies. (shrink)

In this précis I summarise the main ideas of my book Philosophy of Psychedelics. The book discusses philosophical issues arising from the therapeutic use of “classic” psychedelic drugs such as psilocybin and LSD. The book is organised around what I call the Comforting Delusion Objection to psychedelic therapy: the concern that this novel and promising treatment relies essentially on the induction of non-naturalistic metaphysical beliefs, rendering it epistemically objectionable. I begin the précis by summarizing material from chapters two and (...) three of the book, which review evidence for the therapeutic efficacy of psychedelics, and the facts about their clinical use that prompt the Comforting Delusion Objection. I then summarize materials from chapters four and five of the book, which argue that psychedelic therapy works neither by experience-independent processes of neuroplasticity, nor by inducing non-naturalistic metaphysical ideations, but by altering mental representations of the self. Next, I summarise the specific, speculative account of how this might work that is developed in chapters six and seven of the book. This account is based on the predictive processing theory of brain function and the self-binding theory of self-representation. Chapters eight and nine of the book argue, on the basis of this account, that psychedelic therapy can have significant epistemic and spiritual benefits that are compatible with a naturalistic worldview. I summarize this material, and then, finally, the overall conclusions about psychedelic therapy drawn in the tenth and final chapter of the book. (shrink)

“Classic”, serotonergic psychedelic drugs such as LSD and psilocybin are the objects of renewed attention in science and psychiatry. A recent spate of research has produced evidence that psychedelics might be safe and effective adjuncts to the treatment of mood and addictive disorders, agents of positive psychological change in healthy subjects, and valuable tools for studying the neural mechanisms of perception and cognition. This chapter surveys three philosophical debates that have arisen in response to this “renaissance” of psychedelic research. (...) The first concerns the mechanisms of psychedelic-assisted psychotherapy (“psychedelic therapy”): How, exactly, does psychedelic administration in controlled conditions cause lasting psychological benefits? The second concerns the implications of psychedelic research for the philosophy of mind: Does psychedelic evidence show that there can be conscious mental states lacking all forms of self-consciousness? The third concerns the epistemic status of the psychedelic state: Is it possible that certain kinds of knowledge, or other epistemic benefits, could be gained by undergoing a psychedelic experience? (shrink)

Recent evidence shows significant potential for therapies involving psychedelic substances such as psilocybin and MDMA to improve clinical outcomes for patients experiencing various mental disorders. However, research to date focuses almost exclusively on adults. I argue that adolescents should be included in research into psychedelic therapies. First, I demonstrate the pressing need for novel interventions to address the growing mental health burden of adolescents, and I draw on empirical evidence to show that research into psychedelic therapies presents an opportunity (...) to address this shortfall. Secondly, I argue that psychedelics pose low risk to young patients, particularly relative to existing psychiatric medications. I then address two major concerns specific to adolescent contexts. First, I address the risks of using psychedelic substances at earlier stages of physiological and cognitive development. I note that the lack of understanding of the risks underscores the need for including adolescents in research. I then address the added complexity of consent in the adolescent context. I highlight some additional concerns that should be addressed in an “enhanced” informed consent process for adolescents and defend the view that capable adolescents should be able to consent to psychedelic interventions. I ultimately hold that including adolescents in emerging psychedelic research has the potential to substantiate innovative treatments that could improve their clinical outcomes, long-term mental health and quality of life. (shrink)

In recent years, the scientific study of meditation and psychedelic drugs has seen remarkable developments. The increased focus on meditation in cognitive neuroscience has led to a cross-cultural classification of standard meditation styles validated by functional and structural neuroanatomical data. Meanwhile, the renaissance of psychedelic research has shed light on the neurophysiology of altered states of consciousness induced by classical psychedelics, such as psilocybin and LSD, whose effects are mainly mediated by agonism of serotonin receptors. Few attempts have been (...) made at bridging these two domains of inquiry, despite intriguing evidence of overlap between the phenomenology and neurophysiology of meditation practice and psychedelic states. In particular, many contemplative traditions explicitly aim at dissolving the sense of self by eliciting altered states of consciousness through meditation, while classical psychedelics are known to produce significant disruptions of self-consciousness, a phenomenon known as drug-induced ego dissolution. In this article, we discuss available evidence regarding convergences and differences between phenomenological and neurophysiological data on meditation practice and psychedelic drug-induced states, with a particular emphasis on alterations of self-experience. While both meditation and psychedelics may disrupt self-consciousness and underlying neural processes, we emphasize that neither meditation nor psychedelic states can be conceived as simple, uniform categories. Moreover, we suggest that there are important phenomenological differences even between conscious states described as experiences of self-loss. As a result, we propose that self-consciousness may be best construed as a multidimensional construct, and that “self-loss,” far from being an unequivocal phenomenon, can take several forms. Indeed, various aspects of self-consciousness, including narrative aspects linked to autobiographical memory, self-related thoughts and mental time travel, and embodied aspects rooted in multisensory processes, may be differently affected by psychedelics and meditation practices. Finally, we consider long-term outcomes of experiences of self-loss induced by meditation and psychedelics on individual traits and prosocial behavior. We call for caution regarding the problematic conflation of temporary states of self-loss with “selflessness” as a behavioral or social trait, although there is preliminary evidence that correlations between short-term experiences of self-loss and long-term trait alterations may exist. (shrink)

The urgent need for solutions to critical environmental challenges is well attested, but often environmental problems are understood as fundamentally collective action problems. However, to solve to these problems, there is also a need to change individual behavior. Hence, there is a pressing need to inculcate in individuals the environmental virtues — virtues of character that relate to our environmental place in the world. We propose a way of meeting this need, by the judicious, safe, and controlled administration of “classic” (...) psychedelic drugs as a way to catalyze the development of environmental virtues – a form of moral bio-enhancement. Recent evidence shows that psychedelics can be given safely in controlled environments, and can induce vivid experiences of unity and connectedness. These experiences, in turn, can durably increase feelings of nature-relatedness and pro-environmental behaviors. Therefore, we argue that responsible psychedelic use can reliably catalyze the development of a key environmental virtue known as living in place. This is a “master environmental virtue” that subsumes the qualities of respect for nature, proper humility, and aesthetic wonder and awe. Our account advances the environmental virtues debate by introducing a relevant practical proposal, and advances the psychedelic moral enhancement debate by providing a much-needed conceptual framework. (shrink)

In this opinion piece we propose the investigation of psychedelic-assisted psychotherapy for the treatment of body dysmorphic disorder (BDD). BDD is a psychiatric disorder characterised by appearance-based preoccupations and accompanying compulsions. While safe and effective treatments for BDD exist, non-response and relapse rates remain high. Therefore, there is a need to investigate promising new treatment options for this highly debilitating condition. Preliminary evidence suggests safety, feasibility, and potential efficacy of psychedelic treatments in disorders that share similar psychopathological mechanisms with BDD. (...) Drawing on this evidence, as well as on relevant qualitative reports and theoretical proposals, we argue that it would be worthwhile to conduct a phase 2a study aimed at assessing the safety and feasibility of psychedelic-assisted psychotherapy in BDD. We also offer some suggestions for how future research ought to proceed. (shrink)

Induced by intake of the psychedelic substances LSD, psilocybin, DMT and mescaline, psychedelic experiences have been extensively described by subjects as entailing a most unusual increase in the scope and quality of their consciousness. Accordingly, psychedelic experiences have been widely characterised as an “expansion of consciousness.” This article poses the following question, as yet unaddressed in contemporary philosophy and the tradition of phenomenology: to what exactly does “expansion of consciousness” refer as a general characterisation of psychedelic experiences, and what (...) role might attention play therein? On the basis of Aron Gurwitsch’s phenomenology of attention, the following thesis is presented: (a) “expansion of consciousness” refers to a particular restructuration of consciousness in psychedelic experiences. (b) This occurs by means of certain extreme transformations in direction, scope, mode and degree of attention. In order to explicate this thesis, the characteristic features of psychedelic experiences that pertain to expansion of consciousness and attention are first systematically identified from a survey of subject reports. Second, it is demonstrated that the few previous attempts to understand expansion of consciousness in terms of attention as a filter/reducing-valve, spotlight or zoom-lens each fail to explain how consciousness is structured in psychedelic experiences. Third, it is argued that psychedelic expansion of consciousness is a general restructuration of consciousness by means of extreme attentional transformations. In conclusion, brief consideration is given to the question of whether psychedelic expansion of consciousness can have epistemic and ethical value for life. (shrink)

In light of new historical evidence regarding ethnomycologist R. Gordon Wasson’s correspondence with art historian Erwin Panofsky, this article provides an in-depth analysis of the presence of entheogenic mushroom images in Christian art within the context of the controversy between Wasson and philologist John Marco Allegro over the identification of a Garden of Eden fresco in the 12th century Chapel of Plaincourault in France. It reveals a compelling financial motive for Wasson’s refusal to acknowledge that this fresco represents Amanita muscaria, (...) as well as for Wasson’s reluctance to pursue his hypothesis regarding the entheogenic origins of religion into Christian art and artifacts. While Wasson’s view – that the presence of psychoactive mushrooms in the Near and Middle East ended around 1000 BCE – prevailed and stymied research on entheogens in Christianity for decades, a new generation of 21st century researchers has documented growing evidence of A. muscaria and psilocybin-containing mushrooms in Christian art, consistent with ethnobotanist Giorgio Samorini’s typology of mushroom trees. This article presents original photographs, taken during fieldwork at churches and cathedrals throughout Europe and the Middle East, that confirm the presence of entheogenic mushrooms in Christian art: in frescoes, illuminated manuscripts, mosaics, sculptures, and stained glass windows. Based on this iconic evidence, the article proposes a psychedelic gospels theory and addresses critiques of this theory by art historians, ardent advocates, medieval historians, and conservative Catholics. It calls for the establishment of an Interdisciplinary Committee on the Psychedelic Gospels to independently evaluate the growing body of evidence of entheogenic mushrooms in Christian art in order to resolve a controversial question regarding the possible role of entheogens in the history and origins of Christianity. (shrink)

Several authors have recently suggested that classic psychedelics might be safe and effective agents of moral enhancement. This raises the question: can we learn anything interesting about the nature of moral experience from a close examination of transformative psychedelic experiences? The interdisciplinary enterprise of philosophical psychopathology attempts to learn about the structure and function of the “ordinary” mind by studying the radically altered mind. By analogy, in this chapter we argue that we can gain knowledge about the everyday moral life (...) by studying extraordinary experiences of altered moral cognition and experience. We focus on a specific class of cases: experiences of forgiveness induced by psychedelics. We argue that close attention to such experiences reveals the importance of thought/emotion coherence and dissonance in the moral life and vindicates some heterodox ideas about moral phenomenology and psychology. (shrink)

Users of psychedelic drugs often report that their sense of being a self or ‘I’ distinct from the rest of the world has diminished or altogether dissolved. Neuroscientific study of such ‘ego dissolution’ experiences offers a window onto the nature of self-awareness. We argue that ego dissolution is best explained by an account that explains self-awareness as resulting from the integrated functioning of hierarchical predictive models which posit the existence of a stable and unchanging entity to which representations are bound. (...) Combining recent work on the ‘integrative self' and the phenomenon of self-binding with predictive processing principles yields an explanation of ego dissolution according to which self-representation is a useful Cartesian fiction: an ultimately false representation of a simple and enduring substance to which attributes are bound which serves to integrate and unify cognitive processing across levels and domains. The self-model is not a mere narrative posit, as some have suggested; it has a more robust and ubiquitous cognitive function than that. But this does not mean, as others have claimed, that the self-model has the right attributes to qualify as a self. It performs some of the right kinds of functions, but it is not the right kind of entity. Ego dissolution experiences reveal that the self-model plays an important binding function in cognitive processing, but the self does not exist. (shrink)

Psychedelic ingestion and meditative practice are both ancient methods for altering consciousness that became widely known in Western society in the second half of the 20th century. Do the similarities begin and end there, or do these methods – as many have claimed over the years – share some deeper common elements? In this chapter I take a neurophilosophical approach to this question and argue that there are, indeed, deeper commonalities. Recent empirical studies show that psychedelics and meditation modulate overlapping (...) brain networks involved in the sense of self, salience, and attention; moreover, psychedelics can occasion lasting increases in “mindfulness-related capacities” for taking a non-reactive stance on one’s inner experience (e.g. Sampedro et al. 2017). The self-binding theory of psychedelic ego dissolution (Letheby and Gerrans 2017) offers a plausible explanation of these findings: by disrupting self-related beliefs implemented in high-level cortical networks, both psychedelics and meditation can “unbind” mental contents from one’s self-model, moving these contents along the continuum from phenomenal transparency to opacity (cf. Metzinger 2003). In other words, both psychedelics and meditation can expose and weaken our foundational beliefs about our own identity, allowing us to disidentify with these beliefs and see them as “just thoughts”. There are connections between these ideas and recent arguments suggesting that psychedelic use may have epistemic benefits consistent with philosophical naturalism (Letheby 2015, 2016, 2019). I conclude with a proposal: these connections may help in thinking about the putative epistemic benefits of meditation practice from a naturalistic perspective. (shrink)

Recent scientific research suggests that altered states of consciousness induced by classic psychedelic drugs can cause durable psychological benefits in both healthy and patient populations. The phenomenon of ‘psychedelic transformation’ has many philosophically provocative aspects, not least of which is the claim commonly made by psychedelic subjects that their transformation is centrally due to some kind of learning or knowledge gain. Can psychedelic experiences really be a source of knowledge? From the vantage point of philosophical materialism or naturalism, a negative (...) answer is tempting because psychedelic subjects often claim drug-facilitated knowledge of non-natural, transcendent realities. This fact, combined with common conceptions of these drugs as ‘hallucinogenic’ or ‘psychotomimetic’, invites the conclusion that claims of epistemic benefit from psychedelic experience are uniformly false. However, several recent proposals have been made in the literature about naturalistically acceptable epistemic benefits that might arise from psychedelic use. In this chapter I review these proposals, classifying them in accordance with standard epistemological categories, and discuss the arguments for and against them. I also offer some suggestions for future research. (shrink)

Ketamine is a well-known and widely available general anesthetic from the 1960s that, in sub-anesthetic doses, has been adopted in a limited manner for the treatment of acute suicidality and treatment-resistant depression. Its short onset time and short duration of action make it feasible for use at outpatient clinics. In the US, it has a long history of off-label use and was officially approved for depression treatment in 2019. In Finland, it has been administered to selected hospitalized patients in the (...) public healthcare system since 2010 and became available at a private outpatient clinic very recently. In Norway, it has been administered off-label at a private clinic for approximately 500 patients since mid-2010s and at a public clinic for approximately 300 patients since 2020, with plans on opening more clinics in 2024. In the US, the treatment has been administered to hundreds of thousands of patients. -/- The retrospective ethnographic inquiry part of this study features a Finnish woman in her twenties who suffered from treatment-resistant depression, rooted in her insecure childhood and having been bullied at school, as well as income insecurity and excessive workload in adulthood. Eventually, she was violently raped, which induced an obvious post-traumatic stress disorder and exacerbated her depression, incapacitating her. In the course of approximately five years, she was prescribed ten different anti-depressive medications and seventeen other medications, including various antipsychotic medications and lithium. These failed to provide an anti-depressive effect but resulted in 'massive' adverse effects instead, including 60% weight gain and psychotic hallucinations. Eventually, esketamine spray treatment at a private outpatient clinic resolved her depression in a single session. A weekly re-administration process was ongoing. -/- In this case, repeated esketamine administration alleviated depression by producing accumulating corrective emotional experiences without the need to re-experience previous traumatizing events. In a few months to a year, the transient but accumulating anti-depressive effect typically leads to the resolution of depression in most cases, if the patients' living conditions no longer constantly re-traumatize them. It is necessary to adopt ketamine more widely as an emergency measure while more effective, non-addictive alternatives and complements are prepared for adoption. The cost of this specific pilot program implementation was unscalable, but costs can be reduced by approximately 90% by modifying the implementation details. Ketamine and its more effective alternative, 5-MeO-DMT, can serve a major role in facilitating a rebirth of public and private mental healthcare systems, with treatment efficacy multiplied and treatment costs simultaneously reduced. (shrink)

Serotonergic (or “classic”) psychedelics have struck many researchers as raising significant philosophical questions that, until recently, were largely unexplored by academic philosophers. This paper provides an overview of four emerging lines of research at the intersection of academic philosophy and psychedelic science that have gained considerable traction in the last decade: selfless consciousness, psychedelic epistemology, psychedelic ethics, and spiritual/religious naturalism. In this paper, we highlight philosophical questions concerning (i) psychedelics, self-consciousness, and phenomenal consciousness, (ii) the epistemic profile of the psychedelic (...) experience; (iii) ethical concerns about the appropriate use of psychedelics; and (iv) whether spiritual or religious dimensions of psychedelic use are compatible with a naturalistic worldview. (shrink)