The Associations of Naturalistic Classic Psychedelic Use, Mystical Experience, and Creative Problem Solving

Feel connected to create: Self-reported psychedelic drug users exhibit higher sense of connectedness and better divergent thinking skills compared to non-users

Psychedelic drugs can increase health, wellbeing, and even boost cognitive functions such as creativity. Beyond this, previous studies indicated that psychedelic drug intake can increase the sense of connectedness to the world, to others, and to the self. The present preregistered cross-sectional online survey investigated whether the link between psychedelic drug use and creativity (as a potential and real-life creativity) takes place due to the increased sense of connectedness in psychedelic drug users. We collected data of 326 participants (187 psychedelic users and 139 non-users), who worked on an alternate uses task and answered questionnaires assessing real-life creativity, sense of connectedness, the experience of meaningful coincidences, as well as life satisfaction and affect. In line with all preregistered hypotheses, we found that psychedelic drug users showed a higher sense of connectedness, higher creative potential (i.e., originality, fluency), and more creative activities (at a trend). Furthermore, feelings of connectedness (to the self and to the world) were associated with the originality of ideas and real-life creativity, and connectedness to the self partially mediated the difference in the originality of ideas between the psychedelic drug users and non-users. Life satisfaction and positive affect were not significantly higher in psychedelic users but were positively linked to connectedness, creativity, and to synchronicity experiences. These findings provide evidence for the association between self-reported psychedelic drug use and creativity and strengthen the role of connectedness (to the self) as a potential psychological reason why psychedelics might enhance creativity.

The road to Aha: A recipe for mental breakthroughs

We present a novel framework for understanding the diverse spectrum of mental breakthrough events, ranging from problem-solving insights to profound personal transformations. We propose that these events, while varied in expression and impact, share common underlying mechanisms of representational change. We also hypothesise that the differences in phenomenological intensity can be conceptualized along a continuum. Central to our model are three core components - tension, altered salience, and enhanced flexibility - which we identify as essential prerequisites for significant cognitive restructuring. These components interact within an iterative cycle, influencing both the emergence and nature of insight experiences. Drawing on examples from different fields, we explore how a conflict between existing models can trigger this cycle, wherein mechanisms of attention allocation and relaxation of constraints work in tandem to facilitate the emergence of insights. Furthermore, we propose that the intensity of the "aha-moment" and the breadth of its impact are contingent on how central the conflict is within one's conceptual landscape and the extent to which existing mental models are challenged. Thus, the model accounts for both the subtle, momentary insights in problem-solving and the transformative realizations that reshape core beliefs and self-perception. By synthesising insights from various domains, including psychotherapy, contemplative science, and psychedelic research, we present a theoretical account with broad scope, aiming to shed light on the complex processes that can lead to a wide array of mental breakthroughs, thereby contributing to the understanding of insight phenomena across disciplines.

From taboo to treatment: The emergence of psychedelics in the management of pain and opioid use disorder

The rise of psychedelics in contemporary medicine has sparked interest in their potential therapeutic applications. While traditionally associated with countercultural movements and recreational use, recent research has shed light on the potential benefits of psychedelics in various mental health conditions. In this review, we explore the possible role of psychedelics in the management of chronic pain and opioid use disorder (OUD), 2 critical areas in need of innovative treatment options. Pain control remains a significant clinical challenge, particularly for individuals with OUD and those who receive long-term opioid therapy who develop marked tolerance to opioid-induced analgesia. Despite the magnitude of this problem, there is a scarcity of controlled studies investigating pain management alternatives for these populations. Drawing from preclinical and human evidence, we highlight the potential of psychedelics to act on shared neurobiological substrates of chronic pain and OUD, potentially reversing pain- and opioid-induced neuroadaptations, such as central sensitization. We elaborate on the multifaceted dimensions of the pain experience (sensory, affective and cognitive) and their intersections that overlap with opioid-related phenomena (opioid craving and withdrawal), hypothesizing how these processes can be modulated by psychedelics. After summarizing the available clinical research, we propose mechanistic insights and methodological considerations for the design of future translational studies and clinical trials, building on a shared clinical and neurobiological understanding of chronic pain and OUD. Our intention is to provide timely perspectives that accelerate the development and exploration of novel therapeutics for chronic pain and OUD amidst the escalating opioid crisis.

Are psychedelic medicines the reset for chronic pain? Preliminary findings and research needs

Chronic pain is a leading cause of disability, reduced productivity, healthcare seeking, and a contributor to opioid overdose in the United States. For many people, pain can be satisfactorily managed by existing medicines and comprehensive psychosocial treatments. For others, available treatments are either ineffective or not acceptable due to side effects and concerns about risks. Preliminary evidence suggests that some psychedelics may be effective for certain types of pain and/or improved quality of life with increased functionality and reduced disability and distress in people whose pain may never be completely relieved. Efficacy in these quality-of-life related outcomes would be consistent with the "reset in thinking" about chronic pain management increasingly called for as a more realistic goal for some people than complete elimination of pain. This commentary summarizes the rationale for conducting more basic research and clinical trials to further explore the potential for psychedelics in chronic pain management. And, if shown to be effective, to determine whether the effects of psychedelics are primarily due to direct antinociceptive or anti-inflammatory mechanisms, or via increased tolerability, acceptance, and sense of spirituality, that appear to at least partially mediate the therapeutic effects of psychedelics observed in psychiatric disorders such as major depression. This commentary represents a collaboration of clinical and more basic scientists examining these issues and developing recommendations for research ranging from neuropharmacology to the biopsychosocial treatment factors that appear to be as important in pain management as in depression and other disorders in which psychedelic medicines are under development.

Modalities of the psychedelic experience: Microclimates of set and setting in hallucinogen research and culture

Mid-20th-century American research on psychedelics evinced a stunning diversity of interpretations of hallucinogenic effects. While some researchers viewed psychedelics as invaluable tools for psychotherapy, others persisted in treating them as psychosis-inducing agents. As some groups considered psychedelics as catalysts for artistic creativity, others investigated their potential use as psychochemical weapons in the battlefield, or conversely as tools for spiritual ecstasy and revelation. This bewildering array of perceptions regarding the nature of hallucinogenic effects led to stark contrasts in the contexts (set and setting) of psychedelic research and experimentation, leading to wildly divergent outcomes and reports on the effects of the drugs, and strident disagreements between the actors in the field. Examining this remarkable historical moment of epistemological unclarity regarding psychedelics and their effects, this article describes how distinct scientific and cultural trends and moments of mid-20th-century America contributed to the creation of diverse microclimates of set and setting that reproduced investigator beliefs and attitudes and brought about a beguiling Pygmalion effect that left researchers befuddled and perplexed. I propose the concept of psychedelic modality to describe how distinct sociocultural microclimates lead to thematic aggregates in which distinct types of expectations, intentions as well as physical, social, and cultural environments all tend to cluster, producing characteristic outcomes and results. By exploring the historical context and consequences of the emergence of seven psychedelic modalities (psychotomimetic, military, psychotherapeutic, spiritual, artistic-creative, tech-innovative, and political) in mid-20th-century America, this article outlines the varieties of psychedelic experiences in their relationship with culture at large, and subcultures in particular.

Self-Entropic Broadening Theory: Toward a New Understanding of Self and Behavior Change Informed by Psychedelics and Psychosis

The extremes of human experiences, such as those occasioned by classic psychedelics and psychosis, provide a rich contrast for understanding how components of these experiences impact well-being. In recent years, research has suggested that classic psychedelics display the potential to promote positive enduring psychologic and behavioral changes in clinical and nonclinical populations. Paradoxically, classic psychedelics have been described as psychotomimetics. This review offers a putative solution to this paradox by providing a theory of how classic psychedelics often facilitate persistent increases in well-being, whereas psychosis leads down a "darker" path. This will be done by providing an overview of the overlap between the states (i.e., entropic processing) and their core differences (i.e., self-focus). In brief, entropic processing can be defined as an enhanced overall attentional scope and decreased predictability in processing stimuli facilitating a hyperassociative style of thinking. However, the outcomes of entropic states vary depending on level of self-focus, or the degree to which the associations and information being processed are evaluated in a self-referential manner. We also describe potential points of overlap with less extreme experiences, such as creative thinking and positive emotion-induction. Self-entropic broadening theory offers a heuristically valuable perspective on classic psychedelics and their lasting effects and relation to other states by creating a novel synthesis of contemporary theories in psychology. SIGNIFICANCE STATEMENT: Self-entropic broadening theory provides a novel theory examining the psychedelic-psychotomimetic paradox, or how classic psychedelics can be therapeutic, yet mimic symptoms of psychosis. It also posits a framework for understanding the transdiagnostic applicability of classic psychedelics. We hope this model invigorates the field to provide more rigorous comparisons between classic psychedelic-induced states and psychosis and further examinations of how classic psychedelics facilitate long-term change. As a more psychedelic future of psychiatry appears imminent, a model that addresses these long-standing questions is crucial.

A Dose of Creativity: An Integrative Review of the Effects of Serotonergic Psychedelics on Creativity

This integrative review was conducted to summarize the knowledge pertaining to the effects that serotonergic psychedelics can have on creativity, a multi-dimensional construct referring to the ability to produce original and valuable artifacts. Psychedelics, which have long been hailed as substances that can enhance the creative process in their users, have experienced a recent resurgence in research, allowing the opportunity to better understand this relationship. To this end, I reviewed literature which attempted to study the effects of serotonergic psychedelics on creativity through psychometric methods. A total of eleven studies were reviewed, with four psychedelic compounds represented. Every study assessed components and subcomponents of divergent and convergent thinking, with only one instance of product assessment. Results suggest that convergent thinking may increase during the post-acute phases of the drugs' intake, fostering the capacity for development of previously generated ideas. However, this evidence may be circumstantial based on the low number of studies available, small sample sizes, overall lack of randomized controlled trials, and significant methodological limitations throughout most studies. Potential mechanisms underlying these effects are discussed, along with the current state of the research and implications for future studies.

Psychedelics, Sociality, and Human Evolution

Our hominin ancestors inevitably encountered and likely ingested psychedelic mushrooms throughout their evolutionary history. This assertion is supported by current understanding of: early hominins' paleodiet and paleoecology; primate phylogeny of mycophagical and self-medicative behaviors; and the biogeography of psilocybin-containing fungi. These lines of evidence indicate mushrooms (including bioactive species) have been a relevant resource since the Pliocene, when hominins intensified exploitation of forest floor foods. Psilocybin and similar psychedelics that primarily target the serotonin 2A receptor subtype stimulate an active coping strategy response that may provide an enhanced capacity for adaptive changes through a flexible and associative mode of cognition. Such psychedelics also alter emotional processing, self-regulation, and social behavior, often having enduring effects on individual and group well-being and sociality. A homeostatic and drug instrumentalization perspective suggests that incidental inclusion of psychedelics in the diet of hominins, and their eventual addition to rituals and institutions of early humans could have conferred selective advantages. Hominin evolution occurred in an ever-changing, and at times quickly changing, environmental landscape and entailed advancement into a socio-cognitive niche, i.e., the development of a socially interdependent lifeway based on reasoning, cooperative communication, and social learning. In this context, psychedelics' effects in enhancing sociality, imagination, eloquence, and suggestibility may have increased adaptability and fitness. We present interdisciplinary evidence for a model of psychedelic instrumentalization focused on four interrelated instrumentalization goals: management of psychological distress and treatment of health problems; enhanced social interaction and interpersonal relations; facilitation of collective ritual and religious activities; and enhanced group decision-making. The socio-cognitive niche was simultaneously a selection pressure and an adaptive response, and was partially constructed by hominins through their activities and their choices. Therefore, the evolutionary scenario put forward suggests that integration of psilocybin into ancient diet, communal practice, and proto-religious activity may have enhanced hominin response to the socio-cognitive niche, while also aiding in its creation. In particular, the interpersonal and prosocial effects of psilocybin may have mediated the expansion of social bonding mechanisms such as laughter, music, storytelling, and religion, imposing a systematic bias on the selective environment that favored selection for prosociality in our lineage.

New Insights Into the Clinical and Nonclinical Effects of Psychedelic Substances

Abstract. After decades of stagnation, research on psychedelic substances (such as lysergic acid diethylamide [LSD], psilocybin, or N,N-dimethyltryptamine [DMT]) has experienced a renaissance over the last 10 years, with various major research programs being conducted across Europe and the United States. This research primarily investigates the potential of psychedelics in the treatment of mental health disorders, their short- and long-term effects on recreational users, and the neurological and cognitive processes responsible for their effects. The present review provides a concise summary of the most recent insights gained from this research. We briefly outline the history of psychedelic research, the objective and subjective effects caused by these substances, the prevalence and socio-psychological correlates of their use, as well as their potential for harm. Subsequently, we review empirical research on the beneficial effects of psychedelics in clinical samples, focusing on their efficacy in the treatment of major depression, anxiety, and substance use disorders, and discuss research on the proposed neural and cognitive mechanisms behind these effects. We then review research on their effects on healthy subjects, focusing on psychological well-being as well as changes in personality, nature-relatedness, and creativity. Finally, we review empirical evidence regarding the long-term effects of single experiences with psychedelics and conclude with a summary and outlook.

Does Psychedelic Therapy Have a Transdiagnostic Action and Prophylactic Potential?

Addressing global mental health is a major 21st-century challenge. Current treatments have recognized limitations; in this context, new ones that are prophylactic and effective across diagnostic boundaries would represent a major advance. The view that there exists a core of transdiagnostic overlap between psychiatric disorders has re-emerged in recent years, and evidence that psychedelic therapy holds promise for a range of psychiatric disorders supports the position that it may be transdiagnostically effective. Here, we propose that psychedelic therapy's core, transdiagnostically relevant action lies in its ability to increase neuronal and mental plasticity, thus enhancing the potential for change, which we consider to be a key to its therapeutic benefits. Moreover, we suggest that enhanced plasticity via psychedelics, combined with a psychotherapeutic approach, can aid healthy adaptability and resilience, which are protective factors for long-term well-being. We present candidate neurological and psychological markers of this plasticity and link them with a predictive processing model of the action of psychedelics. We propose that a model of psychedelic-induced plasticity combined with an adequate therapeutic context has prophylactic and transdiagnostic potential, implying that it could have a broad, positive impact on public health.

Psychedelics and potential benefits in “healthy normals”: A review of the literature

We are in the midst of a psychedelic research renaissance. With research examining the efficacy of psychedelics as a treatment for a range of mental health indications still in its early stages, there is an increasing body of research to show that careful use of psychedelics can yield a variety of benefits in “healthy normals” and so lead to “the betterment of well people.” Psychedelics have been found to modulate neuroplasticity, and usage in a supportive setting can result in enduring increases in traits such as well-being, life satisfaction, life meaning, mindfulness, and a variety of measures associated with prosocial behaviors and healthy psychological functioning. The effect of psychedelic experience on measures of personality trait openness and is potential implications is examined, and the potential role of awe as a mediator of the benefits of the psychedelic experience is discussed. Special attention is given to the capacity of psychedelics to increase measures of nature relatedness in an enduring sense, which is being correlated with a broad range of measures of psychological well-being as well as a key predictor of pro-environmental awareness and behavior. The effects of particular classical psychedelic compounds on healthy people are discussed, with special attention given to the mystical-type experiences occasioned by high doses of psychedelics, which appear to be an important mediator of long-term benefits and psychotherapeutic gains. Research looking at the potential benefits of psychedelic microdosing is discussed. Potential future research avenues are explored, focusing on the potential development of psychedelics as agents of ecotherapy.

Twenty percent better with 20 micrograms? A qualitative study of psychedelic microdosing self-rapports and discussions on YouTube

BACKGROUND

Psychedelic microdosing is the trending practice of using tiny repeated doses of psychedelic substances to facilitate a range of supposed benefits. With only a few published studies to date, the subject is still under-researched, and more knowledge is warranted. Social media and internet discussion forums have played a vital role in the growing visibility of the microdosing phenomenon, and the present study utilized YouTube contents to improve comprehension of the microdosing practice as well as the social interactions and discussions around microdosing.

METHODS

Microdosing self-disclosure in YouTube videos and their following comments were qualitatively analyzed by inductive thematic analysis. Various software was utilized to enable gathering and sorting relevant data.

RESULTS

Microdosing of psychedelic substances, primarily LSD and psilocybin, was used for therapeutic and enhancement purposes, and predominantly beneficial effects were reported. Many different applications and outcomes were discussed, and therapeutic effects for depression appeared especially noteworthy. Intentions for use were recognized as an influencing factor for the progression and outcomes of microdosing. The function of social interactions was mainly to discuss views on the microdosing phenomenon, strategies for optimal results, minimize risks, and share emotional support.

CONCLUSIONS

Potentially, microdosing could provide some of the same benefits (for certain conditions) as full-dose interventions with less risk of adverse reactions related to the sometimes intense experiences of higher doses. Microdosing may well also mean additional benefits, as well as risks, through the repeated exposure over extended periods.

Classic psychedelics: the special role of the visual system

Here, we briefly overview the various aspects of classic serotonergic hallucinogens reported by a number of studies. One of the key hypotheses of our paper is that the visual effects of psychedelics might play a key role in resetting fears. Namely, we especially focus on visual processes because they are among the most prominent features of hallucinogen-induced hallucinations. We hypothesize that our brain has an ancient visual-based (preverbal) intrinsic cognitive process that, during the transient inhibition of top-down convergent and abstract thinking (mediated by the prefrontal cortex) by psychedelics, can neutralize emotional fears of unconscious and conscious life experiences from the past. In these processes, the decreased functional integrity of the self-referencing processes of the default mode network, the modified multisensory integration (linked to bodily self-consciousness and self-awareness), and the modified amygdala activity may also play key roles. Moreover, the emotional reset (elimination of stress-related emotions) by psychedelics may induce psychological changes and overwrite the stress-related neuroepigenetic information of past unconscious and conscious emotional fears.

Understanding Central Nervous System Effects of Deliriant Hallucinogenic Drugs through Experimental Animal Models

Hallucinogenic drugs potently alter human behavior and have a millennia-long history of use for medicinal and religious purposes. Interest is rapidly growing in their potential as CNS modulators and therapeutic agents for brain conditions. Antimuscarinic cholinergic drugs, such as atropine and scopolamine, induce characteristic hyperactivity and dream-like hallucinations and form a separate group of hallucinogens known as "deliriants". Although atropine and scopolamine are relatively well-studied drugs in cholinergic physiology, deliriants represent the least-studied class of hallucinogens in terms of their behavioral and neurological phenotypes. As such, novel approaches and new model organisms are needed to investigate the CNS effects of these compounds. Here, we comprehensively evaluate the preclinical effects of deliriant hallucinogens in various animal models, their mechanisms of action, and potential interplay with other signaling pathways. We also parallel experimental and clinical findings on deliriant agents and outline future directions of translational research in this field.

Positive psychology in the investigation of psychedelics and entactogens: A critical review

RATIONALE

We reviewed the concepts and empirical findings in studies with psychedelics and entactogens related to positive psychology - the study of healthy human functioning, well-being and eudaemonia. It is an unresolved question how beneficial effects of psychedelics and entactogens are related to the potential risks of these substances - particularly in non-clinical settings.

METHODS

We searched in PubMed, PsychINFO and the Cochrane Library for controlled clinical and epidemiological studies which applied concepts from positive psychology. We included N = 77 eligible studies with 9876 participants published before November 1st, 2017: (1) quantitative studies (N = 54), (2) preliminary or exploratory studies and reviews not including meta-analyses (N = 17), and (3) studies evidencing primarily negative results (N = 6).

RESULTS

Positive psychology concepts have been applied for measuring effects of clinical trials, recreational and ceremonial use of psychedelics and entactogens. Psychedelics and entactogens were shown to produce acute and long-term effects on mood, well-being, prosocial behaviours, empathy, cognitive flexibility, creativity, personality factors like openness, value orientations, nature-relatedness, spirituality, self-transcendence and mindfulness-related capabilities.

CONCLUSIONS

There is preliminary evidence for beneficial effects of psychedelics and entactogens on measures of positive psychology in clinical and healthy populations, however their sustainability remains largely unresolved. The reported results must be considered preliminary due to methodological restrictions. Since longitudinal data on both positive and adverse effects of psychedelics are lacking, more rigorous and standardized measures from positive psychology should be applied in less biased populations with prospective longitudinal designs to carefully assess the benefit-risk-ratio. This article is part of the Special Issue entitled 'Psychedelics: New Doors, Altered Perceptions'.

Dreams and Psychedelics: Neurophenomenological Comparison and Therapeutic Implications

BACKGROUND

A resurgence of neurobiological and clinical research is currently underway into the therapeutic potential of serotonergic or 'classical' psychedelics, such as the prototypical psychedelic drug lysergic acid diethylamide (LSD), psilocybin (4-phosphoryloxy-N,Ndimethyltryptamine), and ayahuasca - a betacarboline- and dimethyltryptamine (DMT)-containing Amazonian beverage. The aim of this review is to introduce readers to the similarities and dissimilarities between psychedelic states and night dreams, and to draw conclusions related to therapeutic applications of psychedelics in psychiatry.

METHODS

Research literature related to psychedelics and dreaming is reviewed, and these two states of consciousness are systematically compared. Relevant conclusions with regard to psychedelicassisted therapy will be provided.

RESULTS

Common features between psychedelic states and night dreams include perception, mental imagery, emotion activation, fear memory extinction, and sense of self and body. Differences between these two states are related to differential perceptual input from the environment, clarity of consciousness and meta-cognitive abilities. Therefore, psychedelic states are closest to lucid dreaming which is characterized by a mixed state of dreaming and waking consciousness.

CONCLUSION

The broad overlap between dreaming and psychedelic states supports the notion that psychedelics acutely induce dreamlike subjective experiences which may have long-term beneficial effects on psychosocial functioning and well-being. Future clinical studies should examine how therapeutic outcome is related to the acute dreamlike effects of psychedelics.

Unifying Theories of Psychedelic Drug Effects

How do psychedelic drugs produce their characteristic range of acute effects in perception, emotion, cognition, and sense of self? How do these effects relate to the clinical efficacy of psychedelic-assisted therapies? Efforts to understand psychedelic phenomena date back more than a century in Western science. In this article I review theories of psychedelic drug effects and highlight key concepts which have endured over the last 125 years of psychedelic science. First, I describe the subjective phenomenology of acute psychedelic effects using the best available data. Next, I review late 19th-century and early 20th-century theories-model psychoses theory, filtration theory, and psychoanalytic theory-and highlight their shared features. I then briefly review recent findings on the neuropharmacology and neurophysiology of psychedelic drugs in humans. Finally, I describe recent theories of psychedelic drug effects which leverage 21st-century cognitive neuroscience frameworks-entropic brain theory, integrated information theory, and predictive processing-and point out key shared features that link back to earlier theories. I identify an abstract principle which cuts across many theories past and present: psychedelic drugs perturb universal brain processes that normally serve to constrain neural systems central to perception, emotion, cognition, and sense of self. I conclude that making an explicit effort to investigate the principles and mechanisms of psychedelic drug effects is a uniquely powerful way to iteratively develop and test unifying theories of brain function.

Powerful substances in tiny amounts: An interview study of psychedelic microdosing

Aims:

This article presents a qualitative interview study of people who microdose with psychedelic drugs, which means that the user takes about one tenth of an ordinary recreational dose.

Design:

Respondents (n = 21) were recruited at several Internet fora for individual interviews via private messaging. Every participant was male, and the median respondent was in his 30s with a stable job and relationship and extensive entheogen experience.

Results:

Respondents tended to experiment with microdosing in phases, reporting mostly positive consequences from this form of drug use. Reported effects included improved mood, cognition, and creativity, which often served to counteract symptoms especially from conditions of anxiety and depression. There were also reports of various challenges with psychedelic microdosing, and some did not find the practice worth continuing.

Conclusion:

The study obtained evidence of a group of users taking small doses of psychedelics not for the purpose of intoxication but to enhance everyday functioning. While the study’s findings are not generalisable, they may inform subsequent investigations with research questions and hypotheses.

Dreamlike effects of LSD on waking imagery in humans depend on serotonin 2A receptor activation

RATIONALE

Accumulating evidence indicates that the mixed serotonin and dopamine receptor agonist lysergic acid diethylamide (LSD) induces an altered state of consciousness that resembles dreaming.

OBJECTIVES

This study aimed to test the hypotheses that LSD produces dreamlike waking imagery and that this imagery depends on 5-HT2A receptor activation and is related to subjective drug effects.

METHODS

Twenty-five healthy subjects performed an audiorecorded guided mental imagery task 7 h after drug administration during three drug conditions: placebo, LSD (100 mcg orally) and LSD together with the 5-HT2A receptor antagonist ketanserin (40 mg orally). Cognitive bizarreness of guided mental imagery reports was quantified as a standardised formal measure of dream mentation. State of consciousness was evaluated using the Altered State of Consciousness (5D-ASC) questionnaire.

RESULTS

LSD, compared with placebo, significantly increased cognitive bizarreness (p < 0.001). The LSD-induced increase in cognitive bizarreness was positively correlated with the LSD-induced loss of self-boundaries and cognitive control (p < 0.05). Both LSD-induced increases in cognitive bizarreness and changes in state of consciousness were fully blocked by ketanserin.

CONCLUSIONS

LSD produced mental imagery similar to dreaming, primarily via activation of the 5-HT2A receptor and in relation to loss of self-boundaries and cognitive control. Future psychopharmacological studies should assess the differential contribution of the D2/D1 and 5-HT1A receptors to cognitive bizarreness.