Double-blind comparison of the two hallucinogens psilocybin and dextromethorphan: similarities and differences in subjective experiences

The compulsive eating paradigm: can psychedelics help in treating obesity?

Obesity is a multifactorial disorder involving a behavioural aetiology in subsets of patients that traditional therapeutic approaches have failed to address. Drawing parallels with addiction, the rewarding aspects of a chronic energy-dense diet can compromise dopaminergic reward circuits, eventually causing individuals to become habitually responsive to food-related stimuli despite adverse health consequences. The maladaptive prediction of reward and motivational salience that becomes associated with food-related stimuli can exert top-down influence on perception and attention, promoting compulsive eating behaviour. Emerging research suggests that psychedelics, e.g., psilocybin and LSD, induce non-ordinary mental states where the influence of such behaviours could potentially be reduced and modified. Based on current evidence, mechanisms have been proposed which suggest that psychedelics might relax the top-down influence of high-level predictions encoded within neuronal hierarchies and sensitise them to bottom-up information flow. Additionally, psychedelics are thought to open a window of psychological flexibility, allowing people to potentially become open to new cognitive and behavioural strategies that can be offered via assisted psychotherapy. Therefore, psychedelics-assisted psychotherapy may encourage beneficial changes to eating behaviour, in those with maladaptive eating habits. While promising in theory, new research is needed to assess the potential efficacy of psychedelics-assisted psychotherapy in treating compulsive eating behaviour.

Insights on psychedelics: A systematic review of therapeutic effects

BACKGROUND

Insight - a sudden change in understanding or perspective that feels true or reliable - is a common occurrence during psychedelic experiences, and often considered by clinicians and patients to be central to their therapeutic value. However, their occurrence and role has not been systematically assessed.

OBJECTIVES

We reviewed all peer-reviewed studies that published data on insight catalysed by a classic psychedelic at psychoactive levels to elucidate several aspects of psychedelic-catalysed insight, including its prevalence, relationship to dose, time-course, and relationship to therapeutic outcomes. Risk of bias was assessed regarding selection, reliability, causality, and transparency. PROSPERO registration: CRD42023405854 FINDINGS: The final database and key bibliography searches were completed on July 13, 2024. We screened 741 abstracts and included 98 studies (40 survey, 58 interventional). Insight was positively correlated with psychedelic dose, and was significantly higher following psychedelics in 43 of 46 (93 %) studies that presented a comparison to a placebo condition. Crucially, 25 of 29 studies (86 %) found that insight was associated with therapeutic improvement, and this relationship was often stronger than mystical-type experience, which has received more research attention.

INTERPRETATION

This review indicates that psychedelic-catalysed insight is associated with therapeutic improvement, suggesting its importance for clinical practice and for understanding the mechanisms of psychedelic therapy.

LIMITATIONS

Heterogeneous study designs and operationalisations of insight precluded a meta-analytic summary. Publication bias and selective reporting is possible, given insight was typically not a primary outcome of the included studies.

Modifying Informed Consent to Help Address Functional Unmasking in Psychedelic Clinical Trials

Importance

There is unprecedented clinician, industry, and patient interest in the therapeutic development of psychedelic drugs. This is due to a combination of promising clinical trial results, positive media coverage, and the lack of novel pharmacologic treatments for psychiatric disorders in recent decades. However, the field faces a key methodological challenge: masking participants to treatment conditions in psychedelic clinical trials has been largely unsuccessful.

Objective

When participants can tell whether they received active drug or placebo, their responses to clinical assessments, questionnaires, and even their functional imaging and biological data can be influenced by preconceptions about treatment effects. Positive patient expectancies combined with ineffective masking may skew outcomes and inflate effect sizes. This complicates efforts to determine the safety and efficacy of psychedelic drugs. Here, we explore a method to help address this problem: modifying informed consent to obscure information about the study design.

Evidence Review

We reviewed all contemporary (2000-2024) clinical trials of psychedelic or methylenedioxymethamphetamine (MDMA) therapy and corresponded with the investigators to compile information on the use of modifications to informed consent in these studies.

Findings

Modifying informed consent to obscure details of the study design has been implemented in several psychedelic clinical trials and may offer a way to strengthen masking. However, this approach poses significant ethical risks. We examine examples of modifications used in the psychedelic literature, discuss the current regulatory landscape, and suggest strategies to mitigate risks associated with modified informed consent.

Conclusions and Relevance

Incorporating modified informed consent in future psychedelic clinical trials may improve interpretability and impact, but this has not been explicitly tested. Modifications to informed consent may not be appropriate in all cases, and risks to participants should be minimized by implementing appropriate guardrails.

Synergistic, multi-level understanding of psychedelics: three systematic reviews and meta-analyses of their pharmacology, neuroimaging and phenomenology

Serotonergic psychedelics induce altered states of consciousness and have shown potential for treating a variety of neuropsychiatric disorders, including depression and addiction. Yet their modes of action are not fully understood. Here, we provide a novel, synergistic understanding of psychedelics arising from systematic reviews and meta-analyses of three hierarchical levels of analysis: (1) subjective experience (phenomenology), (2) neuroimaging and (3) molecular pharmacology. Phenomenologically, medium and high doses of LSD yield significantly higher ratings of visionary restructuralisation than psilocybin on the 5-dimensional Altered States of Consciousness Scale. Our neuroimaging results reveal that, in general, psychedelics significantly strengthen between-network functional connectivity (FC) while significantly diminishing within-network FC. Pharmacologically, LSD induces significantly more inositol phosphate formation at the 5-HT2A receptor than DMT and psilocin, yet there are no significant between-drug differences in the selectivity of psychedelics for the 5-HT2A, 5-HT2C, or D2 receptors, relative to the 5-HT1A receptor. Our meta-analyses link DMT, LSD, and psilocybin to specific neural fingerprints at each level of analysis. The results show a highly non-linear relationship between these fingerprints. Overall, our analysis highlighted the high heterogeneity and risk of bias in the literature. This suggests an urgent need for standardising experimental procedures and analysis techniques, as well as for more research on the emergence between different levels of psychedelic effects.

Learning how to make use of dissociative therapies

Dissociative therapies are being increasingly explored for their psychiatric applications, although questions remain about how they work and how best to use them. In exploring these questions, this review highlights six key areas of clinical relevance: (1) The possible contributions of functional unblinding when interpreting efficacy data; (2) The degree to which the therapeutic effects of dissociative therapies can be distinguished from the transient forms of relief seen with recreational drug use; (3) Understanding the construct of dissociation as it is tasked with describing the function of dissociative drugs; (4) The investigation of subjective drug effects as predictors of therapeutic outcome; (5) Similarities and differences in the effects of dissociative and classic psychedelics; and (6) The anticipated need for judicious prescribing/deprescribing resources as dissociative therapies proliferate.

Considering distinct positive emotions in psychedelic science

In this review, we discuss psychedelics' acute subjective and persisting therapeutic effects, outline the science of positive emotions, and highlight the value in considering distinct positive emotions in psychedelic science. Psychedelics produce a wide variety of acute subjective effects (i.e. the 'trip'), including positive emotions and affective states such as awe and joy. However, despite a rich literature on distinct emotions and their different correlates and sequelae, distinct emotions in psychedelic science remain understudied. Insofar as psychedelics' acute subjective effects may play a role in their downstream therapeutic effects (e.g. decreased depression, anxiety, and substance misuse), considering the role of distinct positive emotions in psychedelic experiences has the potential to yield more precise statements about psychedelic-related subjective processes and outcomes. We propose here that understanding the role of positive emotions within the context of psychedelic experiences could help elucidate the connection between psychedelics' acute subjective effects and therapeutic outcomes.

The Role of Music in Psychedelic-Assisted Therapy: A Comparative Analysis of Neuroscientific Research, Indigenous Entheogenic Ritual, and Contemporary Care Models

Music is deeply rooted in the human experience as well as a fundamental part of psychedelic-assisted therapies (PAT) and entheogenic ceremonies. Although a large body of research exists highlighting the importance of music from rehabilitative, psychological, neurobiological, anthropological, religious, and sociological contexts, there is limited scientific literature regarding the specific relevance of music in PAT and indigenous entheogenic ritual as a means of enhancing clinical outcomes. As demand for mental health services continues to grow and awareness of the medicinal benefits of psychedelic substances to treat mental and neurological conditions increases, a new wave of interest has emerged to support the development of care models, including how music is used during PAT. Music is a reliable cornerstone in therapeutic and ritualistic spaces using psychedelics, however there is still an immense opportunity to cultivate PAT models with interdisciplinary, evidence-informed perspectives and thoughtful analysis of music use in treatment. To contribute to this development, this review evaluates neuroscientific, psychological, and anthropological research on the neural and cognitive underpinnings of music as well as music use with psychedelics both in modern research settings and indigenous entheogenic ceremonies. In addition, personalized approaches to music protocols in PAT, how music use in traditional rituals may help inform best practices, and the need for researchers to specify music protocols in treatment models are detailed. Consideration of carefully respecting the bridging of indigenous practices and current medical models is discussed to highlight areas for future development.

Prospective Preference Assessment for the Psilocybin for Enhanced Analgesia in Chronic nEuropathic PAIN (PEACE-PAIN) Trial

Background

Negative perceptions of psilocybin and challenges of participant enrollment may represent barriers to conducting a randomized controlled trial examining psilocybin for chronic neuropathic pain.

Aim

Prior to trial initiation, we aimed to examine patient attitudes toward the trial via a prospective preference assessment.

Methods

Twenty-six patients with chronic neuropathic pain participated in a prospective preference assessment comprising quantitative (survey) and qualitative (interview) components. Content analysis was used to inductively and deductively identify factors that would motivate or discourage participation in the proposed trial. Demographics, clinical characteristics, and perceptions of psilocybin were collected to explore differences in characteristics between patients who were willing and unwilling to participate.

Results

Survey results showed that most participants (76.9%) were willing to participate in the PEACE-PAIN trial. "Willing" participants reported higher prior psychedelic use (75%) as compared to the "maybe willing" (0%) and "not willing" participants (0%). Interviews indicated that the top two factors that motivated participation included the need for new treatment options (31.7%) and benefits to personal pain management (31.7%). The top two discouraging factors included practical difficulties of research participation (16.7%), and adverse events associated with psilocybin (16.7%).

Conclusions

The PEACE-PAIN trial study design is supported by patient survey responses but may benefit from modifications, namely incorporating thorough discussions of the current evidence for efficacy, safety, tolerability, and approaches to address adverse effects of psilocybin. Additionally, the interest in participation by individuals with prior psychedelic use holds important methodological implications for the inclusion/exclusion criteria of the trial.

Enhanced visual contrast suppression during peak psilocybin effects: Psychophysical results from a pilot randomized controlled trial

In visual perception, an effect known as surround suppression occurs wherein the apparent contrast of a center stimulus is reduced when it is presented within a higher-contrast surrounding stimulus. Many key aspects of visual perception involve surround suppression, yet the neuromodulatory processes involved remain unclear. Psilocybin is a serotonergic psychedelic compound known for its robust effects on visual perception, particularly texture, color, object, and motion perception. We asked whether surround suppression is altered under peak effects of psilocybin. Using a contrast-matching task with different center-surround stimulus configurations, we measured surround suppression after 25 mg of psilocybin compared with placebo (100 mg niacin). Data on harms were collected, and no serious adverse events were reported. After taking psilocybin, participants (n = 6) reported stronger surround suppression of perceived contrast compared to placebo. Furthermore, we found that the intensity of subjective psychedelic visuals induced by psilocybin correlated positively with the magnitude of surround suppression. We note the potential relevance of our findings for the field of psychiatry, given that studies have demonstrated weakened visual surround suppression in both major depressive disorder and schizophrenia. Our findings are thus relevant to understanding the visual effects of psilocybin, and the potential mechanisms of visual disruption in mental health disorders.

RE104: Synthesis and Activity of a Novel Serotonergic Psychedelic Prodrug of 4-Hydroxy-N,N-diisopropyltryptamine

Results from randomized clinical trials of psilocybin in depressive disorders highlight the therapeutic potential of serotonergic psychedelic compounds in mental health disorders. The synthetic 5-hydroxytryptamine 2A receptor agonist 4-hydroxy-N,N-diisopropyltryptamine (4-OH-DiPT) is structurally similar to psilocin but is reported to have a shorter duration (2-3 h) of psychedelic effects, suggesting the potential for psilocybin-like therapeutic activity with reduced clinical resource burden. Here, we describe the preclinical and translational characterization of RE104, a 4-OH-DiPT prodrug comprising a glutarate moiety designed to cleave rapidly in situ and thus provide reasonable bioavailability of the active drug. Plasma concentration of 4-HO-DiPT over time in PK experiments in rats was correlated with head-twitch intensity. The half-life of 4-OH-DiPT was 40 min after subcutaneous administration of RE104 in rats. In a forced swim test, a single dose of RE104 (1 mg/kg) significantly reduced mean immobility time at 1 week compared with vehicle (P < 0.001), confirming translational antidepressant potential. Taken together, these data with RE104 show that the glutarate ester can act as an efficient prodrug strategy for 4-HO-DiPT, a unique short-duration psychedelic with potential in depressive disorders.

Efficacy of psilocybin for treating symptoms of depression: systematic review and meta-analysis

OBJECTIVE

To determine the efficacy of psilocybin as an antidepressant compared with placebo or non-psychoactive drugs.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Five electronic databases of published literature (Cochrane Central Register of Controlled Trials, Medline, Embase, Science Citation Index and Conference Proceedings Citation Index, and PsycInfo) and four databases of unpublished and international literature (ClinicalTrials.gov, WHO International Clinical Trials Registry Platform, ProQuest Dissertations and Theses Global, and PsycEXTRA), and handsearching of reference lists, conference proceedings, and abstracts.

DATA SYNTHESIS AND STUDY QUALITY

Information on potential treatment effect moderators was extracted, including depression type (primary or secondary), previous use of psychedelics, psilocybin dosage, type of outcome measure (clinician rated or self-reported), and personal characteristics (eg, age, sex). Data were synthesised using a random effects meta-analysis model, and observed heterogeneity and the effect of covariates were investigated with subgroup analyses and metaregression. Hedges’ g was used as a measure of treatment effect size, to account for small sample effects and substantial differences between the included studies’ sample sizes. Study quality was appraised using Cochrane’s Risk of Bias 2 tool, and the quality of the aggregated evidence was evaluated using GRADE guidelines.

ELIGIBILITY CRITERIA

Randomised trials in which psilocybin was administered as a standalone treatment for adults with clinically significant symptoms of depression and change in symptoms was measured using a validated clinician rated or self-report scale. Studies with directive psychotherapy were included if the psychotherapeutic component was present in both experimental and control conditions. Participants with depression regardless of comorbidities (eg, cancer) were eligible.

RESULTS

Meta-analysis on 436 participants (228 female participants), average age 36-60 years, from seven of the nine included studies showed a significant benefit of psilocybin (Hedges’ g=0.66, 95% confidence interval (CI) 0.46 to 0.86, P<0.001) on change in depression scores compared with comparator treatment. Exploratory subgroup analyses and metaregressions indicated that having secondary depression (Hedges’ g=0.88, 95% CI 0.42 to 1.33), being assessed with self-report depression scales such as the Beck depression inventory (0.88, 0.42 to 1.33), and older age and previous use of psychedelics (metaregression coefficient 0.13, 95% CI 0.02 to 0.23 and 6.00, 2.48 to 9.53, respectively) were correlated with greater improvements in symptoms. All studies had a moderate risk of bias, but the change from baseline metric was associated with low heterogeneity and a statistically non-significant risk of small study bias, resulting in a moderate certainty of evidence rating.

CONCLUSION

Treatment effects of psilocybin were significantly larger among patients with secondary depression, when self-report scales were used to measure symptoms of depression, and when participants had previously used psychedelics. Further research is thus required to delineate the influence of expectancy effects, moderating factors, and treatment delivery on the efficacy of psilocybin as an antidepressant.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42023388065.

Efficacy and safety of psychedelics for the treatment of mental disorders: A systematic review and meta-analysis

We aim to systematically review and meta-analyze the effectiveness and safety of psychedelics [psilocybin, ayahuasca (active component DMT), LSD and MDMA] in treating symptoms of various mental disorders. Web of Science, Embase, EBSCO, and PubMed were searched up to February 2024 and 126 articles were finally included. Results showed that psilocybin has the largest number of articles on treating mood disorders (N = 28), followed by ayahuasca (N = 7) and LSD (N = 6). Overall, psychedelics have therapeutic effects on mental disorders such as depression and anxiety. Specifically, psilocybin (Hedges' g = -1.49, 95% CI [-1.67, -1.30]) showed the strongest therapeutic effect among four psychedelics, followed by ayahuasca (Hedges' g = -1.34, 95% CI [-1.86, -0.82]), MDMA (Hedges' g = -0.83, 95% CI [-1.33, -0.32]), and LSD (Hedges' g = -0.65, 95% CI [-1.03, -0.27]). A small amount of evidence also supports psychedelics improving tobacco addiction, eating disorders, sleep disorders, borderline personality disorder, obsessive-compulsive disorder, and body dysmorphic disorder. The most common adverse event with psychedelics was headache. Nearly a third of the articles reported that no participants reported lasting adverse effects. Our analyses suggest that psychedelics reduce negative mood, and have potential efficacy in other mental disorders, such as substance-use disorders and PTSD.

Pharmaco-toxicological effects of the novel tryptamine hallucinogen 5-MeO-MiPT on motor, sensorimotor, physiological, and cardiorespiratory parameters in mice-from a human poisoning case to the preclinical evidence

RATIONALE

The 5-methoxy-N-methyl-N-isopropyltryptamine (5-MeO-MiPT, known online as "Moxy") is a new psychedelic tryptamine first identified on Italian national territory in 2014. Its hallucinogen effects are broadly well-known; however, only few information is available regarding its pharmaco-toxicological effects.

OBJECTIVES

Following the seizure of this new psychoactive substances by the Arm of Carabinieri and the occurrence of a human intoxication case, in the current study we had the aim to characterize the in vivo acute effects of systemic administration of 5-MeO-MiPT (0.01-30 mg/kg i.p.) on sensorimotor (visual, acoustic, and overall tactile) responses, thermoregulation, and stimulated motor activity (drag and accelerod test) in CD-1 male mice. We also evaluated variation on sensory gating (PPI, prepulse inhibition; 0.01-10 mg/kg i.p.) and on cardiorespiratory parameters (MouseOx and BP-2000; 30 mg/kg i.p.). Lastly, we investigated the in silico ADMET (absorption, distribution, metabolism, excretion, toxicity) profile of 5-MeO-MiPT compared to 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) and N,N-dimethyltryptamine (DMT).

RESULTS

This study demonstrates that 5-MeO-MiPT dose-dependently inhibits sensorimotor and PPI responses and, at high doses, induces impairment of the stimulated motor activity and cardiorespiratory changes in mice. In silico prediction shows that the 5-MeO-MiPT toxicokinetic profile shares similarities with 5-MeO-DIPT and DMT and highlights a cytochrome risk associated with this compound.

CONCLUSIONS

Consumption of 5-MeO-MiPT can affect the ability to perform activities and pose a risk to human health status, as the correspondence between the effects induced in mice and the symptoms occurred in the intoxication case suggests. However, our findings suggest that 5-MeO-MiPT should not be excluded from research in the psychiatric therapy field.

Psychedelic Therapy: A Primer for Primary Care Clinicians-Psilocybin

BACKGROUND

The primary psychoactive drug in magic mushrooms, psilocybin, induces profound alterations in consciousness through the 5-HT2A receptor. This review consolidates current research findings to elucidate the pharmacology, safety profile, and clinical applications of psilocybin.

AREAS OF UNCERTAINTY

Despite initial concerns that psilocybin could cause psychosis, contemporary research has demonstrated that psilocybin is generally safe. The most common adverse effects are nausea and headache, yet both tend to be transient. Serious adverse events can generally be avoided in controlled settings such as clinical trials. However, in the largest clinical trial to date, there were a total of 7 reported cases of suicidal ideation, up to 12 weeks after receiving a single 25 mg dose of psilocybin. That being said, all 7 cases did not respond to the treatment. Although selective serotonin reuptake inhibitors may blunt the hallucinogenic qualities of psilocybin, preliminary research suggests that they may enhance its antidepressant effects.

THERAPEUTIC ADVANCES

In clinical trials, psilocybin has shown promise for treating major depressive disorder and treatment-resistant depression. Initial studies indicated that 42%-57% of patients underwent remission after psilocybin-assisted therapy, which suggests that psilocybin is more effective than existing antidepressant medications. Clinical data have also demonstrated that psilocybin can manage substance use disorders and end-of-life anxiety with clinical outcomes that are sustained for months and sometimes years after 1 or 2 doses.

LIMITATIONS

However, larger Phase II trials with more than 100 depressed participants have shown a much smaller remission rate of 25%-29%, though these studies still observed that psilocybin causes a significant reduction in depressive symptoms.

CONCLUSIONS

Aside from ketamine, psilocybin is the most clinically well-researched psychedelic drug, with trials that have enrolled hundreds of participants and multiple therapeutic applications. Phase III trials will determine whether psilocybin lives up to the promise that it showed in previous clinical trials.

Cardiovascular safety of psychedelic medicine: current status and future directions

Psychedelics are powerful psychoactive substances that alter perception and mood processes. Their effectiveness in the treatment of psychiatric diseases was known before their prohibition. An increasing number of recent studies, due to the indisputable resurgence of serotonergic hallucinogens, have shown their efficacy in alleviating depression, anxiety, substance abuse therapies, and existential distress treatment in patients facing life-threatening illness. Psychedelics are generally considered to be physiologically safe with low toxicity and low addictive potential. However, their agonism at serotonergic receptors should be considered in the context of possible serotonin-related cardiotoxicity (5-HT2A/2B and 5-HT4 receptors), influence on platelet aggregation (5-HT2A receptor), and their proarrhythmic potential. The use of psychedelics has also been associated with significant sympathomimetic effects in both experimental and clinical studies. Therefore, the present review aims to provide a critical discussion of the cardiovascular safety of psilocybin, d-lysergic acid diethylamide (LSD), N,N-dimethyltryptamine, ayahuasca, and mescaline, based on the results of experimental research and clinical trials in humans. Experimental studies provide inconsistent information on the potential cardiovascular effects and toxicity of psychedelics. Data from clinical trials point to the relative cardiovascular safety of psychedelic-assisted therapies in the population of "healthy" volunteers. However, there is insufficient evidence from therapies carried out with microdoses of psychedelics, and there is still a lack of data on the safety of psychedelics in the population of patients with cardiovascular disease. Therefore, the exact determination of the cardiovascular safety of psychedelic therapies (especially long-term therapies) requires further research.

Double-Blind Comparison of the Two Hallucinogens Dextromethorphan and Psilocybin: Experience-Dependent and Enduring Psychological Effects in Healthy Volunteers

Rationale

N-methyl-D-aspartate receptor-mediated dissociatives and serotonergic hallucinogens are being increasingly used in therapeutic interventions that involve nonordinary states of consciousness and may represent a unique mental health paradigm wherein pharmacologically induced experiences are conducive to psychological well-being.

Objective

The aim of this study was to further understand how the phenomenological and health-promoting effects of high-dose dextromethorphan (DXM) compared to psilocybin in the same participants when administered under experimental conditions that are typical of therapeutic psychedelic trials.

Methods

Single, acute oral doses of DXM (400 mg/70 kg), psilocybin (10, 20, 30 mg/70 kg), and inactive placebo were administered under double-blind and psychologically supportive conditions to 20 healthy participants with histories of hallucinogen use. Ratings of personal meaning, spiritual significance, psychological challenge, and psychological insight attributed to acute drug experiences were assessed 7 h (at session end) and 1 week after each drug administration. Persisting psychological effects were assessed 1 week after each drug administration.

Results

High-dose DXM and psilocybin produced similar increases over placebo in ratings of drug experience that was predictive of psychological benefit at 1 week, even when expectancy effects were minimized. These effects tended to favor psilocybin in a dose-dependent manner and were limited by poor physical tolerability for DXM.

Conclusions

This analysis suggests the utility of exploring clinical applications of dissociatives that occur within the supportive contexts that are characteristic of psychedelic research and that prioritize the optimization of psychologically valuable drug experiences. This study was registered with ClinicalTrials.gov (NCT02033707).

Comparative acute effects of mescaline, lysergic acid diethylamide, and psilocybin in a randomized, double-blind, placebo-controlled cross-over study in healthy participants

Mescaline, lysergic acid diethylamide (LSD), and psilocybin are classic serotonergic psychedelics. A valid, direct comparison of the effects of these substances is lacking. The main goal of the present study was to investigate potential pharmacological, physiological and phenomenological differences at psychoactive-equivalent doses of mescaline, LSD, and psilocybin. The present study used a randomized, double-blind, placebo-controlled, cross-over design to compare the acute subjective effects, autonomic effects, and pharmacokinetics of typically used, moderate to high doses of mescaline (300 and 500 mg), LSD (100 µg), and psilocybin (20 mg) in 32 healthy participants. A mescaline dose of 300 mg was used in the first 16 participants and 500 mg was used in the subsequent 16 participants. Acute subjective effects of 500 mg mescaline, LSD, and psilocybin were comparable across various psychometric scales. Autonomic effects of 500 mg mescaline, LSD, and psilocybin were moderate, with psilocybin causing a higher increase in diastolic blood pressure compared with LSD, and LSD showing a trend toward an increase in heart rate compared with psilocybin. The tolerability of mescaline, LSD, and psilocybin was comparable, with mescaline at both doses inducing slightly more subacute adverse effects (12-24 h) than LSD and psilocybin. Clear distinctions were seen in the duration of action between the three substances. Mescaline had the longest effect duration (mean: 11.1 h), followed by LSD (mean: 8.2 h), and psilocybin (mean: 4.9 h). Plasma elimination half-lives of mescaline and LSD were similar (approximately 3.5 h). The longer effect duration of mescaline compared with LSD was due to the longer time to reach maximal plasma concentrations and related peak effects. Mescaline and LSD, but not psilocybin, enhanced circulating oxytocin. None of the substances altered plasma brain-derived neurotrophic factor concentrations. In conclusion, the present study found no evidence of qualitative differences in altered states of consciousness that were induced by equally strong doses of mescaline, LSD, and psilocybin. The results indicate that any differences in the pharmacological profiles of mescaline, LSD, and psilocybin do not translate into relevant differences in the subjective experience. ClinicalTrials.gov identifier: NCT04227756.

History repeating: guidelines to address common problems in psychedelic science

Research in the last decade has expressed considerable optimism about the clinical potential of psychedelics for the treatment of mental disorders. This optimism is reflected in an increase in research papers, investments by pharmaceutical companies, patents, media coverage, as well as political and legislative changes. However, psychedelic science is facing serious challenges that threaten the validity of core findings and raise doubt regarding clinical efficacy and safety. In this paper, we introduce the 10 most pressing challenges, grouped into easy, moderate, and hard problems. We show how these problems threaten internal validity (treatment effects are due to factors unrelated to the treatment), external validity (lack of generalizability), construct validity (unclear working mechanism), or statistical conclusion validity (conclusions do not follow from the data and methods). These problems tend to co-occur in psychedelic studies, limiting conclusions that can be drawn about the safety and efficacy of psychedelic therapy. We provide a roadmap for tackling these challenges and share a checklist that researchers, journalists, funders, policymakers, and other stakeholders can use to assess the quality of psychedelic science. Addressing today's problems is necessary to find out whether the optimism regarding the therapeutic potential of psychedelics has been warranted and to avoid history repeating itself.

Ecstatic or Mystical Experience through Epilepsy

Ecstatic epilepsy is a rare form of focal epilepsy, so named because the seizures' first symptoms consist of an ecstatic/mystical experience, including feelings of increased self-awareness, mental clarity, and "unity with everything that exists," accompanied by a sense of bliss and physical well-being. In this perspective article, we first describe the phenomenology of ecstatic seizures, address their historical context, and describe the primary brain structure involved in the genesis of these peculiar epileptic seizures, the anterior insula. In the second part of the article, we move onto the possible neurocognitive underpinnings of ecstatic seizures. We first remind the reader of the insula's role in interoceptive processing and consciously experienced feelings, contextualized by the theory of predictive coding. This leads us to hypothesize that temporary disruptions to activity in the anterior insula could interrupt the generation of interoceptive prediction errors, and cause one to experience the absence of uncertainty, and thereby, a sense of bliss. The absence of interoceptive prediction errors would in fact mimic perfect prediction of the body's physiological state. This sudden clarity of bodily perception could explain the ecstatic quality of the experience, as the interoceptive system forms the basis for unified conscious experience. Our alternative hypothesis is that the anterior insula plays an overarching role in the processing of surprise and that the dysfunction caused by the epileptic discharge could interrupt any surprise exceeding expectations, resulting in a sense of complete control and oneness with the environment.

Mechanisms and molecular targets surrounding the potential therapeutic effects of psychedelics

Psychedelics, also known as classical hallucinogens, have been investigated for decades due to their potential therapeutic effects in the treatment of neuropsychiatric and substance use disorders. The results from clinical trials have shown promise for the use of psychedelics to alleviate symptoms of depression and anxiety, as well as to promote substantial decreases in the use of nicotine and alcohol. While these studies provide compelling evidence for the powerful subjective experience and prolonged therapeutic adaptations, the underlying molecular reasons for these robust and clinically meaningful improvements are still poorly understood. Preclinical studies assessing the targets and circuitry of the post-acute effects of classical psychedelics are ongoing. Current literature is split between a serotonin 5-HT2A receptor (5-HT2AR)-dependent or -independent signaling pathway, as researchers are attempting to harness the mechanisms behind the sustained post-acute therapeutically relevant effects. A combination of molecular, behavioral, and genetic techniques in neuropharmacology has begun to show promise for elucidating these mechanisms. As the field progresses, increasing evidence points towards the importance of the subjective experience induced by psychedelic-assisted therapy, but without further cross validation between clinical and preclinical research, the why behind the experience and its translational validity may be lost.

Psilocybin's effects on cognition and creativity: A scoping review

BACKGROUND

Research on psilocybin has become increasingly popular during the current psychedelic renaissance, which began in the early 1990s. Psilocybin's effects on mental health are promising and there are ongoing efforts to investigate its clinical implementation and its effects on cognition.

AIMS

The purpose of this study is to report trends in publications, methods, and findings from research examining the effects of psilocybin on cognition and creativity in adults.

METHODS

We conducted an Open Science Framework preregistered scoping review, guided by the JBI Manual for Evidence Synthesis, on literature pertaining to psilocybin's effects on cognition and creativity.

RESULTS/OUTCOMES

In the 42 included studies, psilocybin was primarily administered orally (83%) in a bodyweight-adjusted manner (74%) to healthy participants (90%). Of the few studies that explicitly reported safety outcomes (26%), only one reported serious adverse reactions. During the acute phase post-intake (i.e., minutes to hours), macrodoses tended to impair cognitive performance and creativity, whereas microdoses tended toward creative enhancement. The few macrodosing studies that included post-acute measures (i.e., 1-85 days) reported primarily null but some positive effects.

CONCLUSIONS/INTERPRETATION

This scoping review identified a time-based variation of psilocybin macrodosing effects on cognition and creativity, in which impairment may be observed early post-intake but withdraw over time, and some positive effects may emerge afterward. These findings are limited by methodological concerns and inadequate assessment of long-term effects. We therefore recommend that future psilocybin research be conducted according to existing guidelines and include well-validated measures of cognition and creativity at multiple timepoints.

Effect of LSD and music on the time-varying brain dynamics

RATIONALE

Psychedelics are getting closer to being widely used in clinical treatment. Music is known as a key element of psychedelic-assisted therapy due to its psychological effects, specifically on the emotion, meaning-making, and sensory processing. However, there is still a lack of understanding in how psychedelics influence brain activity in experimental settings involving music listening.

OBJECTIVES

The main goal of our research was to investigate the effect of music, as a part of "setting," on the brain states dynamics after lysergic acid diethylamide (LSD) intake.

METHODS

We used an open dataset, where a group of 15 participants underwent two functional MRI scanning sessions under LSD and placebo influence. Every scanning session contained three runs: two resting-state runs separated by one run with music listening. We applied K-Means clustering to identify the repetitive patterns of brain activity, so-called brain states. For further analysis, we calculated states' dwell time, fractional occupancy and transition probability.

RESULTS

The interaction effect of music and psychedelics led to change in the time-varying brain activity of the task-positive state. LSD, regardless of the music, affected the dynamics of the state of combined activity of DMN, SOM, and VIS networks. Crucially, we observed that the music itself could potentially have a long-term influence on the resting-state, in particular on states involving task-positive networks.

CONCLUSIONS

This study indicates that music, as a crucial element of "setting," can potentially have an influence on the subject's resting-state during psychedelic experience. Further studies should replicate these results on a larger sample size.

Classics in Chemical Neuroscience: Dextromethorphan (DXM)

Dextromethorphan (DXM) was introduced in 1958 as the first non-opioid cough suppressant and is indicated for multiple psychiatric disorders. It has been the most used over-the-counter cough suppressant since its emergence. However, individuals quickly noticed an intoxicating and psychedelic effect if they ingested large doses. DXM's antagonism at N-methyl-d-aspartate receptors (NMDAr) is thought to underly its efficacy in treating acute cough, but supratherapeutic doses mimic the activity of dissociative hallucinogens, such as phencyclidine and ketamine. In this Review we will discuss DXM's synthesis, manufacturing information, drug metabolism, pharmacology, adverse effects, recreational use, abuse potential, and its history and importance in therapy to present DXM as a true classic in chemical neuroscience.

Intoxication of dogs and cats with common stimulating, hallucinogenic and dissociative recreational drugs

Pets can have accidental, intentional, or malicious exposure to illicit drugs. It is a growing concern over the last decade because there is an increase in usage of illicit drugs in humans and diagnosis is difficult. Owners are often not aware of exposure, or they are reluctant to admit possession of recreational drugs in the household due to potential legal consequences. In addition, illicit drugs sold on the black market are often adulterated with other substances resulting in non-specific clinical presentation and aggravation of symptoms. There are affordable onsite diagnostic tests on the market which could facilitate diagnosis of intoxication with illicit drugs, but they give a lot of false positive results due to low specificity of the tests. In this paper we gathered information about the most common recreational drugs such as amphetamines, methamphetamine, 3,4-methylenedioxy-methamphetamine (MDMA), phencyclidine (PCP), lysergic acid diethylamide (LSD), psilocybin mushrooms and cocaine in terms of toxicokinetic properties, mechanism of toxic action, clinical presentation and treatment in dogs and cats.

Psilocybin for Depression: From Credibility to Feasibility, What's Missing?

Psilocybin has been suggested as a promising transdiagnostic treatment strategy for a wide range of psychiatric disorders. Recent findings showed that psychedelic-assisted/"psycholitic" psychotherapy should provide significant and sustained alleviation of depressive symptoms. However, to date, there have been several study limitations (e.g., small sample sizes, blinding, limited follow-up, highly screened treatment populations) and some health/political issues, including practitioners' experience, lack of standardized protocols, psychedelics' legal status, ethical concerns, and potential psychological/psychopathological/medical untoward effects. The focus here is on a range of clinical and methodological issues, also aiming at outlining some possible suggestions. We are confident that newer evidence, more precise protocols, and eventual reclassification policies may allow a better understanding of the real potential of psilocybin as a transdiagnostic therapeutic molecule.

The Altered States Database: Psychometric data from a systematic literature review

In this paper, we present the development of the Altered States Database (ASDB), an open-science project based on a systematic literature review. The ASDB contains psychometric questionnaire data on subjective experiences of altered states of consciousness (ASC) induced by pharmacological and non-pharmacological methods. The systematic review follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Scientific journal articles were identified through PubMed and Web of Science. We included studies that examined ASC using the following validated questionnaires: Altered States of Consciousness Rating Scale (APZ, 5D-ASC, 11-ASC), Phenomenology of Consciousness Inventory (PCI), Hallucinogen Rating Scale (HRS), or Mystical Experience Questionnaire (MEQ30). The systematic review resulted in the inclusion of a total of 165 journal articles, whereof questionnaire data was extracted and is now available on the Open Science Framework (OSF) website (https://osf.io/8mbru) and on the ASDB website (http://alteredstatesdb.org), where questionnaire data can be easily retrieved and visualized. This data allows the calculation of comparable psychometric values of ASC experiences and of dose-response relationships of substances inducing ASC.

Measurement(s)	Psychometric questionnaire data
Technology Type(s)	Systematic literature review (PRISMA)
Sample Characteristic - Organism	Human

Structure-Activity Relationships for Psilocybin, Baeocystin, Aeruginascin, and Related Analogues to Produce Pharmacological Effects in Mice

4-Phosphoryloxy-N,N-dimethyltryptamine (psilocybin) is a naturally occurring tertiary amine found in many mushroom species. Psilocybin is a prodrug for 4-hydroxy-N,N-dimethyltryptamine (psilocin), which induces psychedelic effects via agonist activity at the serotonin (5-HT) 2A receptor (5-HT2A). Several other 4-position ring-substituted tryptamines are present in psilocybin-containing mushrooms, including the secondary amine 4-phosphoryloxy-N-methyltryptamine (baeocystin) and the quaternary ammonium 4-phosphoryloxy-N,N,N-trimethyltryptamine (aeruginascin), but these compounds are not well studied. Here, we investigated the structure-activity relationships for psilocybin, baeocystin, and aeruginascin, as compared to their 4-acetoxy and 4-hydroxy analogues, using in vitro and in vivo methods. Broad receptor screening using radioligand binding assays in transfected cells revealed that secondary and tertiary tryptamines with either 4-acetoxy or 4-hydroxy substitutions display nanomolar affinity for most human 5-HT receptor subtypes tested, including the 5-HT2A and the serotonin 1A receptor (5-HT1A). The same compounds displayed affinity for 5-HT2A and 5-HT1A in mouse brain tissue in vitro and exhibited agonist efficacy in assays examining 5-HT2A-mediated calcium mobilization and β-arrestin 2 recruitment. In mouse experiments, only the tertiary amines psilocin, psilocybin, and 4-acetoxy-N,N-dimethyltryptamine (psilacetin) induced head twitch responses (ED50 0.11-0.29 mg/kg) indicative of psychedelic-like activity. Head twitches were blocked by 5-HT2A antagonist pretreatment, supporting 5-HT2A involvement. Both secondary and tertiary amines decreased body temperature and locomotor activity at higher doses, the effects of which were blocked by 5-HT1A antagonist pretreatment. Across all assays, the pharmacological effects of 4-acetoxy and 4-hydroxy compounds were similar, and these compounds were more potent than their 4-phosphoryloxy counterparts. Importantly, psilacetin appears to be a prodrug for psilocin that displays substantial serotonin receptor activities of its own.

Brain entropy, fractal dimensions and predictability: A review of complexity measures for EEG in healthy and neuropsychiatric populations

There has been an increasing trend towards the use of complexity analysis in quantifying neural activity measured by electroencephalography (EEG) signals. On top of revealing complex neuronal processes of the brain that may not be possible with linear approaches, EEG complexity measures have also demonstrated their potential as biomarkers of psychopathology such as depression and schizophrenia. Unfortunately, the opacity of algorithms and descriptions originating from mathematical concepts have made it difficult to understand what complexity is and how to draw consistent conclusions when applied within psychology and neuropsychiatry research. In this review, we provide an overview and entry-level explanation of existing EEG complexity measures, which can be broadly categorized as measures of predictability and regularity. We then synthesize complexity findings across different areas of psychological science, namely, in consciousness research, mood and anxiety disorders, schizophrenia, neurodevelopmental and neurodegenerative disorders, as well as changes across the lifespan, while addressing some theoretical and methodological issues underlying the discrepancies in the data. Finally, we present important considerations when choosing and interpreting these metrics.

Psychedelics, placebo effects, and set and setting: Insights from common factors theory of psychotherapy

Psychedelic-assisted treatment is at first glance markedly different in structure and approach from mainstream forms of psychotherapy in the West. A major criticism of clinical psychedelic research rests on the difficulty of executing placebo-controlled studies and distinguishing drug effects from those of the psychotherapeutic container in which psychedelics are typically presented. Detractors also tend to find fault in spiritual or mystical themes that often arise in the context of psychedelic use. Common factors theory of psychotherapy is a useful and extensively studied framework that can help make sense of these issues, and has much to contribute to our understanding of contextual effects that are often discussed in psychedelic literature as "set and setting." In this article, we examine four major contextual "common factors" shared by various healing traditions: 1) the therapeutic relationship; 2) the healing setting; 3) the rationale, conceptual scheme, or myth; and 4) the ritual. We explain how these factors show up in psychedelic-assisted treatment and how they may contribute to therapeutic effects. Lastly, we discuss the implications of these factors for the concept of placebo, and for future research.

A Research Domain Criteria (RDoC)-Guided Dashboard to Review Psilocybin Target Domains: A Systematic Review

BACKGROUND

Preliminary results from randomized controlled studies as well as identified molecular, cellular, and circuit targets of select psychedelics (e.g., psilocybin) suggest that their effects are transdiagnostic. In this review, we exploit the Research Domain Criteria (RDoC) transdiagnostic framework, to synthesize extant literature on psilocybin.

OBJECTIVE

We aimed to identify RDoC-based effects of psilocybin and vistas for future mechanistic and interventional research.

METHODS

A systematic search in electronic databases (i.e., PubMed, Scopus, PsycINFO, and Web of Science) performed in January and February 2021 identified English articles published between 1990 and 2020 reporting the effects of psilocybin on mental health measures. Data from included articles were retrieved and organized according to the RDoC bio-behavioral matrix and its constituent six main domains, namely: positive valence systems, negative valence systems, cognitive systems, social processes, sensorimotor systems, and arousal and regulatory systems.

RESULTS

The preponderance of research with psilocybin has differentially reported beneficial effects on positive valence systems, negative valence system, and social process domains. The data from the included studies support both short-term (23 assessments) and long-term (15 assessments) beneficial effects of psilocybin on the positive valence systems. While 12 of the extracted outcome measures suggest that psilocybin use is associated with increases in the "fear" construct of the negative valence systems domain, 19 findings show no significant effects on this construct, and seven parameters show lowered levels of the "sustained threat" construct in the long term. Thirty-four outcome measures revealed short-term alterations in the social systems' construct namely, "perception and understanding of self," and "social communications" as well as enhancements in "perception and understanding of others" and "affiliation and attachment". The majority of findings related to the cognitive systems' domain reported dyscognitive effects. There have been relatively few studies reporting outcomes of psilocybin on the remaining RDoC domains. Moreover, seven of the included studies suggest the transdiagnostic effects of psilocybin. The dashboard characterization of RDoC outcomes with psilocybin suggests beneficial effects in the measures of reward, threat, and arousal, as well as general social systems.

CONCLUSIONS

Psilocybin possesses a multi-domain effectiveness. The field would benefit from highly rigorous proof-of-mechanism research to assess the effects of psilocybin using the RDoC framework. The combined effect of psilocybin with psychosocial interventions with RDoC-based outcomes is a priority therapeutic vista.

Adverse experiences resulting in emergency medical treatment seeking following the use of magic mushrooms

BACKGROUND

Psilocybin-containing mushrooms are used for recreational, spiritual, self-development and therapeutic purposes. However, physiologically relatively nontoxic, adverse reactions are occasionally reported.

AIMS

This study investigated the 12-month prevalence and nature of magic mushroom-related adverse reactions resulting in emergency medical treatment seeking in a global sample of people reporting magic mushroom use.

METHODS

We use data from the 2017 Global Drug Survey - a large anonymous online survey on patterns of drug use conducted between November 2016 and January 2017.

RESULTS

Out of 9233 past year magic mushroom users, 19 (0.2%) reported having sought emergency medical treatment, with a per-event risk estimate of 0.06%. Young age was the only predictor associated with higher risk of emergency medical presentations. The most common symptoms were psychological, namely anxiety/panic and paranoia/suspiciousness. Poor 'mindset', poor 'setting' and mixing substances were most reported reasons for incidents. All but one respondent returned back to normality within 24 h.

CONCLUSIONS

The results confirm psilocybin mushrooms are a relatively safe drug, with serious incidents rare and short lasting. Providing harm-reduction information likely plays a key role in preventing adverse effects. More research is needed to examine the detailed circumstances and predictors of adverse reactions including rarer physiological reactions.

Pharmacological, neural, and psychological mechanisms underlying psychedelics: A critical review

This paper provides a critical review of several possible mechanisms at different levels of analysis underlying the effects and therapeutic potential of psychedelics. At the (1) biochemical level, psychedelics primarily affect the 5-HT_2A receptor, increase neuroplasticity, offer a critical period for social reward learning, and have anti-inflammatory properties. At the (2) neural level, psychedelics have been associated with reduced efficacy of thalamo-cortical filtering, the loosening of top-down predictive signaling and an increased sensitivity to bottom-up prediction errors, and activation of the claustro-cortical-circuit. At the (3) psychological level, psychedelics have been shown to induce altered and affective states, they affect cognition, induce belief change, exert social effects, and can result in lasting changes in behavior. We outline the potential for a unifying account of the mechanisms underlying psychedelics and contrast this with a model of pluralistic causation. Ultimately, a better understanding of the specific mechanisms underlying the effects of psychedelics could allow for a more targeted therapeutic approach. We highlight current challenges for psychedelic research and provide a research agenda to foster insight in the causal-mechanistic pathways underlying the efficacy of psychedelic research and therapy.

The altered state of consciousness induced by Δ9-THC

Altered states of consciousness (ASC) provide an opportunity for researchers to study the neurophysiological basis of changes in phenomenal experience. Δ9-tetrahydrocannabinol (THC) is the primary psychoactive constituent of cannabis, however whether the effects of THC include ASC features that are shared with other ASC induction mechanisms, such as classical psychedelics, has not been systematically addressed. We used survey (11D-ASC; State Mindfulness), self-report, and natural language processing (NLP) to assess 7.5 and 15 mg oral THC, relative to placebo, in 25 healthy, infrequent cannabis users. THC dose-dependently increased measures of ASC including Insightfulness, and increased ratings of mindfulness and mind-wandering. THC also increased language entropy as previously reported for LSD. Future studies may seek to determine whether reports of increased mindfulness or insight after THC are primarily representative of a psychotomimetic state (i.e., delusional thinking) or conversely, reflect an enhancement of conscious awareness that may be validated empirically.

Self-Actualization and the Integration of Psychedelic Experience: The Mediating Role of Perceived Benefits to Narrative Self-Functioning

There is a growing need in the field of psychedelic science for a unifying perspective of overall well-being to join seemingly disparate findings across clinical and non-clinical populations, and account for the unique role of post-psychedelic integration for promoting benefits. According to the eudaimonic perspective of well-being, the stories we create about who we are (self-insight) and who we can become (personal development) are key aspects of narrative self-functioning that either constrain or facilitate well-being. The present paper draws upon this perspective to investigate the relationship between extent of post-psychedelic integration and optimal well-being ( self-actualization), with perceived benefits to narrative self-functioning ( self-insight and personal development) as a mediator. The data for testing this model was collected from roughly 750 participants recruited from websites and social media forums. Because the sample contained clinical and non-clinical individuals, the model was able to be tested with mental health condition as a moderator. Results indicated that perceived benefits to narrative self-functioning is one pathway through which integration of psychedelic experience may promote optimal well-being for both clinical and non-clinical populations. Exploratory analyses indicated that integration techniques that are more self-referential in nature are the ones that indirectly relate to optimal well-being via perceived benefits. The results of the present study should be interpreted as a preliminary model for future longitudinal research to test, as our cross-sectional methods preclude any causal inferences to be made from these mediation analyses.

Assessing the risk-benefit profile of classical psychedelics: a clinical review of second-wave psychedelic research

RATIONALE

A broad reassessment of the potential benefits of psychedelic drugs has led to the initiation of multiple major clinical trials in an effort to advance their status to become FDA-approved medications, as well as local legislative efforts to legalize or decriminalize their use.

OBJECTIVES

To use recently published data to assess potential risks and benefits of psychedelic drugs as therapeutics, as well as to synthesize what is currently known in order to generate fruitful future research directions.

METHODS

A review of studies conducted since 1991 identified 14 clinical trials of classical psychedelics, including 11 of psilocybin (N = 257 participants), 1 of lysergic acid diethylamide (N = 12 participants), and 2 of ayahuasca (N = 46 participants). Other published studies (e.g., of healthy volunteers, survey studies, case reports, neuroimaging) were also considered for review.

RESULTS

Published studies since 1991 largely support the hypothesis that small numbers of treatments with psychedelic-assisted psychotherapy can offer significant and sustained alleviation to symptoms of multiple psychiatric conditions. No serious adverse events attributed to psychedelic therapy have been reported. Existing studies have several limitations, including small sample sizes, inherent difficulty in blinding, relatively limited follow-up, and highly screened treatment populations.

CONCLUSIONS

Substantial data have been gathered in the past 30 years suggesting that psychedelics are a potent treatment for a variety of common psychiatric conditions, though the ideal means of employing these substances to minimize adverse events and maximize therapeutic effects remains controversial. Unique factors related to study design are vital for clinical researchers in the field to address.

Great Expectations: recommendations for improving the methodological rigor of psychedelic clinical trials

RATIONALE

Psychedelic research continues to garner significant public and scientific interest with a growing number of clinical studies examining a wide range of conditions and disorders. However, expectancy effects and effective condition masking have been raised as critical limitations to the interpretability of the research.

OBJECTIVE

In this article, we review the many methodological challenges of conducting psychedelic clinical trials and provide recommendations for improving the rigor of future research.

RESULTS

Although some challenges are shared with psychotherapy and pharmacology trials more broadly, psychedelic clinical trials have to contend with several unique sources of potential bias. The subjective effects of a high-dose psychedelic are often so pronounced that it is difficult to mask participants to their treatment condition; the significant hype from positive media coverage on the clinical potential of psychedelics influences participants' expectations for treatment benefit; and participant unmasking and treatment expectations can interact in such a way that makes psychedelic therapy highly susceptible to large placebo and nocebo effects. Specific recommendations to increase the success of masking procedures and reduce the influence of participant expectancies are discussed in the context of study development, participant recruitment and selection, incomplete disclosure of the study design, choice of active placebo condition, as well as the measurement of participant expectations and masking efficacy.

CONCLUSION

Incorporating the recommended design elements is intended to reduce the risk of bias in psychedelic clinical trials and thereby increases the ability to discern treatment-specific effects of psychedelic therapy.

Group VR experiences can produce ego attenuation and connectedness comparable to psychedelics

With a growing body of research highlighting the therapeutic potential of experiential phenomenology which diminishes egoic identity and increases one’s sense of connectedness, there is significant interest in how to elicit such ‘self-transcendent experiences’ (STEs) in laboratory contexts. Psychedelic drugs (YDs) have proven particularly effective in this respect, producing subjective phenomenology which reliably elicits intense STEs. With virtual reality (VR) emerging as a powerful tool for constructing new perceptual environments, we describe a VR framework called ‘Isness-distributed’ (Isness-D) which harnesses the unique affordances of distributed multi-person VR to blur conventional self-other boundaries. Within Isness-D, groups of participants co-habit a shared virtual space, collectively experiencing their bodies as luminous energetic essences with diffuse spatial boundaries. It enables moments of ‘energetic coalescence’, a new class of embodied intersubjective experience where bodies can fluidly merge, enabling participants to include multiple others within their self-representation. To evaluate Isness-D, we adopted a citizen science approach, coordinating an international network of Isness-D 'nodes'. We analyzed the results (N = 58) using 4 different self-report scales previously applied to analyze subjective YD phenomenology (the inclusion of community in self scale, ego-dissolution inventory, communitas scale, and the MEQ30 mystical experience questionnaire). Despite the complexities associated with a distributed experiment like this, the Isness-D scores on all 4 scales were statistically indistinguishable from recently published YD studies, demonstrating that distributed VR can be used to design intersubjective STEs where people dissolve their sense of self in the connection to others.

If the doors of perception were cleansed, would chronic pain be relieved? Evaluating the benefits and risks of psychedelics

Psychedelic substances have played important roles in diverse cultures, and ingesting various plant preparations to evoke altered states of consciousness has been described throughout recorded history. Accounts of the subjective effects of psychedelics typically focus on spiritual and mystical-type experiences, including feelings of unity, sacredness, and transcendence. Over the past two decades, there has been increasing interest in psychedelics as treatments for various medical disorders, including chronic pain. Although concerns about adverse medical and psychological effects contributed to their controlled status, contemporary knowledge of psychedelics suggests that risks are relatively rare when patients are carefully screened, prepared, and supervised. Clinical trial results have provided support for the effectiveness of psychedelics in different psychiatric conditions. However, there are only a small number of generally uncontrolled studies of psychedelics in patients with chronic pain (e.g., cancer pain, phantom limb pain, migraine, and cluster headache). Challenges in evaluating psychedelics as treatments for chronic pain include identifying neurobiologic and psychosocial mechanisms of action and determining which pain conditions to investigate. Truly informative proof-of-concept and confirmatory randomized clinical trials will require careful selection of control groups, efforts to minimize bias from unblinding, and attention to the roles of patient mental set and treatment setting. Perspective: There is considerable promise for the use of psychedelic therapy for pain, but evidence-based recommendations for the design of future studies are needed to ensure that the results of this research are truly informative.

Human behavioral pharmacology of psychedelics

The past decade has witnessed a rapid growth of research on the basic science and clinical understanding of psychedelics. This chapter provides an overview of the human behavioral pharmacology of psychedelics focusing on three prototypic classic psychedelics-psilocybin, lysergic acid diethylamide (LSD), and dimethyltryptamine (DMT). A brief historical overview of the classic psychedelics and naming and drug classification is first specified. Next, special considerations in the conduct of human behavioral pharmacology work with psychedelics is described including the role of set and setting, mystical experience measurement, the use of effective blinding and placebos, and the abuse liability of psychedelics. Following, a description of the subjective, physiological, and clinical effects of psilocybin, LSD, and DMT is provided. This body of work clearly documents a unique and complex collection of subjective effects following psychedelic use, both during acute drug administration and as related to long-term behavior change following use. Clinical research demonstrates potential therapeutic utility with early phase clinical trials showing positive and enduring effects in many difficult-to-treat conditions including treatment-resistant depression, alcohol use disorder, and cigarette smoking. Future work in this newly reemerged field is needed to reveal mechanisms of behavior change in psychedelic drug action. Behavioral pharmacology is ultimately well served to provide this direction answering questions at the intersection of environment and pharmacology.

Direct comparison of the acute effects of lysergic acid diethylamide and psilocybin in a double-blind placebo-controlled study in healthy subjects

Growing interest has been seen in using lysergic acid diethylamide (LSD) and psilocybin in psychiatric research and therapy. However, no modern studies have evaluated differences in subjective and autonomic effects of LSD and psilocybin or their similarities and dose equivalence. We used a double-blind, randomized, placebo-controlled, crossover design in 28 healthy subjects (14 women, 14 men) who underwent five 25 h sessions and received placebo, LSD (100 and 200 µg), and psilocybin (15 and 30 mg). Test days were separated by at least 10 days. Outcome measures included self-rating scales for subjective effects, autonomic effects, adverse effects, effect durations, plasma levels of brain-derived neurotrophic factor (BDNF), prolactin, cortisol, and oxytocin, and pharmacokinetics. The doses of 100 and 200 µg LSD and 30 mg psilocybin produced comparable subjective effects. The 15 mg psilocybin dose produced clearly weaker subjective effects compared with both doses of LSD and 30 mg psilocybin. The 200 µg dose of LSD induced higher ratings of ego-dissolution, impairments in control and cognition, and anxiety than the 100 µg dose. The 200 µg dose of LSD increased only ratings of ineffability significantly more than 30 mg psilocybin. LSD at both doses had clearly longer effect durations than psilocybin. Psilocybin increased blood pressure more than LSD, whereas LSD increased heart rate more than psilocybin. However, both LSD and psilocybin showed comparable cardiostimulant properties, assessed by the rate-pressure product. Both LSD and psilocybin had dose-proportional pharmacokinetics and first-order elimination. Both doses of LSD and the high dose of psilocybin produced qualitatively and quantitatively very similar subjective effects, indicating that alterations of mind that are induced by LSD and psilocybin do not differ beyond the effect duration. Any differences between LSD and psilocybin are dose-dependent rather than substance-dependent. However, LSD and psilocybin differentially increased heart rate and blood pressure. These results may assist with dose finding for future psychedelic research.Trial registration: ClinicalTrials.gov identifier: NCT03604744.

Models of psychedelic drug action: modulation of cortical-subcortical circuits

Classic psychedelic drugs such as psilocybin and lysergic acid diethylamide (LSD) have recaptured the imagination of both science and popular culture, and may have efficacy in treating a wide range of psychiatric disorders. Human and animal studies of psychedelic drug action in the brain have demonstrated the involvement of the serotonin 2A (5-HT2A) receptor and the cerebral cortex in acute psychedelic drug action, but different models have evolved to try to explain the impact of 5-HT2A activation on neural systems. Two prominent models of psychedelic drug action (the cortico-striatal thalamo-cortical, or CSTC, model and relaxed beliefs under psychedelics, or REBUS, model) have emphasized the role of different subcortical structures as crucial in mediating psychedelic drug effects. We describe these models and discuss gaps in knowledge, inconsistencies in the literature and extensions of both models. We then introduce a third circuit-level model involving the claustrum, a thin strip of grey matter between the insula and the external capsule that densely expresses 5-HT2A receptors (the cortico-claustro-cortical, or CCC, model). In this model, we propose that the claustrum entrains canonical cortical network states, and that psychedelic drugs disrupt 5-HT2A-mediated network coupling between the claustrum and the cortex, leading to attenuation of canonical cortical networks during psychedelic drug effects. Together, these three models may explain many phenomena of the psychedelic experience, and using this framework, future research may help to delineate the functional specificity of each circuit to the action of both serotonergic and non-serotonergic hallucinogens.

Predictors and potentiators of psychedelic-occasioned mystical experiences

Mystical experiences are often described as being among the most profound and meaningful events of a person’s life. Their occurrence, while a normal but uncommon phenomenon, is reliably occasioned by psychedelic substances under the appropriate conditions, although care is needed around the context of usage to help ensure safe and beneficial experiences. The occurrence of mystical experiences in psychedelic sessions is a key mediator of the sustained psychological benefits reported in both healthy and clinical populations. Certain factors including set and setting, drug dosage, trait absorption, drug type, intention and states of surrender and acceptance all predict or influence the occurrence of mystical experiences. Various additional factors may further contribute to the occurrence and intensity of mystical experiences and enhance their long-term benefits, including music, meditation and spiritual practices and nature-based settings. This review examines these factors and considers how they might be optimised to increase the chances of a mystical experience occurring, while also considering factors that are negatively associated with mystical experiences with suggestions on how these might be mitigated where applicable. Finally, potential future research avenues for furthering our knowledge of psychedelic mystical experiences and how their benefits might be enhanced is suggested. Maximising the potential for the occurrence of mystical experiences is an important aspect of the beneficial application of psychedelics.

Adverse effects of psychedelics: From anecdotes and misinformation to systematic science

BACKGROUND

Despite an increasing body of research highlighting their efficacy to treat a broad range of medical conditions, psychedelic drugs remain a controversial issue among the public and politicians, tainted by previous stigmatisation and perceptions of risk and danger.

OBJECTIVE

This narrative review examines the evidence for potential harms of the classic psychedelics by separating anecdotes and misinformation from systematic research.

METHODS

Taking a high-level perspective, we address both psychological and psychiatric risks, such as abuse liability and potential for dependence, as well as medical harms, including toxicity and overdose. We explore the evidence base for these adverse effects to elucidate which of these harms are based largely on anecdotes versus those that stand up to current scientific scrutiny.

RESULTS

Our review shows that medical risks are often minimal, and that many - albeit not all - of the persistent negative perceptions of psychological risks are unsupported by the currently available scientific evidence, with the majority of reported adverse effects not being observed in a regulated and/or medical context.

CONCLUSIONS

This highlights the importance for clinicians and therapists to keep to the highest safety and ethical standards. It is imperative not to be overzealous and to ensure balanced media reporting to avoid future controversies, so that much needed research can continue.

The clinical pharmacology and potential therapeutic applications of 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT)

5‐methoxy‐N,N‐dimethyltryptamine (5‐MeO‐DMT) is a naturally occurring tryptamine that primarily acts as an agonist at the 5‐HT1A and 5‐HT2A receptors, whereby affinity for the 5‐HT1A subtype is highest. Subjective effects following 5‐MeO‐DMT administration include distortions in auditory and time perception, amplification of emotional states, and feelings of ego dissolution that usually are short‐lasting, depending on the route of administration. Individual dose escalation of 5‐MeO‐DMT reliably induces a “peak” experience, a state thought to be a core predictor of the therapeutic efficacy of psychedelics. Observational studies and surveys have suggested that single exposure to 5‐MeO‐DMT can cause rapid and sustained reductions in symptoms of depression, anxiety, and stress. 5‐MeO‐DMT also stimulates neuroendocrine function, immunoregulation, and anti‐inflammatory processes, which may contribute to changes in mental health outcomes. To date, only one clinical trial has been published on 5‐MeO‐DMT, demonstrating the safety of vaporized dosing up to 18 mg. Importantly, the rapid onset and short duration of the 5‐MeO‐DMT experience may render it more suitable for individual dose‐finding strategies compared with longer‐acting psychedelics. A range of biotech companies has shown an interest in the development of 5‐MeO‐DMT formulations for a range of medical indications, most notably depression. Commercial development will therefore be the most important resource for bringing 5‐MeO‐DMT to the clinic. However, fundamental research will also be needed to increase understanding of the neurophysiological and neural mechanisms that contribute to the potential clinical effects of 5‐MeO‐DMT and its sustainability and dissemination over time. Such studies are less likely to be conducted as part of drug development programs and are more likely to rely on independent, academic initiatives.

Human Cortical Serotonin 2A Receptor Occupancy by Psilocybin Measured Using [11C]MDL 100,907 Dynamic PET and a Resting-State fMRI-Based Brain Parcellation

Psilocybin (a serotonin 2A, or 5-HT2A, receptor agonist) has shown preliminary efficacy as a treatment for mood and substance use disorders. The current report utilized positron emission tomography (PET) with the selective 5-HT2A receptor inverse agonist radioligand [11C]MDL 100,907 (a.k.a. M100,907) and cortical regions of interest (ROIs) derived from resting-state functional connectivity-based brain parcellations in 4 healthy volunteers (2 females) to determine regional occupancy/target engagement of 5-HT2A receptors after oral administration of a psychoactive dose of psilocybin (10 mg/70 kg). Average 5-HT2A receptor occupancy across all ROIs was 39.5% (± 10.9% SD). Three of the ROIs with greatest occupancy (between 63.12 and 74.72% occupancy) were within the default mode network (subgenual anterior cingulate and bilateral angular gyri). However, marked individual variability in regional occupancy was observed across individuals. These data support further investigation of the relationship between individual differences in the acute and enduring effects of psilocybin and the degree of regional 5-HT2A receptor occupancy.

Safety pharmacology of acute LSD administration in healthy subjects

RATIONALE

Lysergic acid diethylamide (LSD) is used in psychiatric and psychological research and investigated as a potential treatment for medical and psychiatric disorders, including depression, anxiety, and cluster headache.

OBJECTIVES

Safety data on clinical safety are available from small studies but not from larger samples. We report safety pharmacology data from a large pooled study sample on acute effects of LSD in healthy subjects.

METHODS

We conducted a pooled analysis of four double-blind, randomized, placebo-controlled, crossover studies that included a total of 83 healthy subjects and 131 single-dose administrations of LSD. LSD administrations were matched to dose groups according to measured LSD peak plasma concentrations to adjust for uncertainties in the correct LSD dose in some studies. Single doses were 25, 50, 100, and 200 µg of LSD base. We investigated subjective effects (self-rated any drug effect, good drug effect, bad drug effect, and anxiety), blood pressure, heart rate, body temperature, duration of the acute LSD response, acute (12 h) and subacute (24 h) adverse effects, reports of flashbacks, and liver and kidney function before and after the studies.

RESULTS

LSD dose-dependently increased subjective, physiologic, and adverse effects. The dose-response curves for the proportions of subjects with a certain amount of a subjective effect were steeper and reached a higher maximum for positive acute subjective effects compared with negative acute subjective effects. Maximal ratings of > 50% good drug effects were reached in 37%, 91%, 96%, and 91% of the LSD administrations at 25, 50, 100, and 200 µg. Maximal ratings of > 50% bad drug effects were reached in 0%, 9%, 27%, 31% at 25, 50, 100, and 200 µg, respectively. Mean ratings of Oceanic Boundlessness were 10%, 25%, 41%, and 44%, and mean ratings of Anxious Ego-Dissolution were 3.4%, 13%, 20%, and 22% at 25, 50, 100, and 200 µg, respectively. The physiologic effects of LSD were moderate. None of the subjects had systolic blood pressure > 180 mmHg at any time. Peak heart rate > 100 beats/min was observed in 0%, 6%, 20%, and 25% of the subjects at 25, 50, 100, and 200 µg, respectively. Maximal heart rates of 129 and 121 beats/min were observed in one subject at the 50 and 200 µg doses, respectively. Peak body temperature > 38° was observed in 0%, 11%, 7%, and 34% at 25, 50, 100, and 200 µg, respectively. Mean acute adverse effect scores on the List of Complaints were 5.6, 9.2, 12, and 13 at 25, 50, 100, and 200 µg, respectively. Kidney and liver function parameters were unaltered. Six subjects reported transient flashback phenomena.

CONCLUSIONS

The single-dose administration of LSD is safe in regard to acute psychological and physical harm in healthy subjects in a controlled research setting.

Psychedelic Therapy's Transdiagnostic Effects: A Research Domain Criteria (RDoC) Perspective

Accumulating clinical evidence shows that psychedelic therapy, by synergistically combining psychopharmacology and psychological support, offers a promising transdiagnostic treatment strategy for a range of disorders with restricted and/or maladaptive habitual patterns of emotion, cognition and behavior, notably, depression (MDD), treatment resistant depression (TRD) and addiction disorders, but perhaps also anxiety disorders, obsessive-compulsive disorder (OCD), Post-Traumatic Stress Disorder (PTSD) and eating disorders. Despite the emergent transdiagnostic evidence, the specific clinical dimensions that psychedelics are efficacious for, and associated underlying neurobiological pathways, remain to be well-characterized. To this end, this review focuses on pre-clinical and clinical evidence of the acute and sustained therapeutic potential of psychedelic therapy in the context of a transdiagnostic dimensional systems framework. Focusing on the Research Domain Criteria (RDoC) as a template, we will describe the multimodal mechanisms underlying the transdiagnostic therapeutic effects of psychedelic therapy, traversing molecular, cellular and network levels. These levels will be mapped to the RDoC constructs of negative and positive valence systems, arousal regulation, social processing, cognitive and sensorimotor systems. In summarizing this literature and framing it transdiagnostically, we hope we can assist the field in moving toward a mechanistic understanding of how psychedelics work for patients and eventually toward a precise-personalized psychedelic therapy paradigm.

Spontaneous Spiritual Awakenings: Phenomenology, Altered States, Individual Differences, and Well-Being

Spontaneous Spiritual Awakenings (SSAs) are subjective experiences characterised by a sudden sense of direct contact, union, or complete nondual merging (experience of oneness) with a perceived ultimate reality, the universe, "God," or the divine. These profound transformative experiences have scarcely been researched, despite extensive anecdotal evidence suggesting their potential to catalyse drastic, long-term, and often positive shifts in perception, world-view, and well-being. The aims of this study were to investigate the phenomenological variances of these experiences, including the potential differences between SSAs and Spontaneous Kundalini Awakenings (SKAs), a subset of awakening experiences that the authors postulate may produce a higher likelihood of both physical and negative effects; to explore how these experiences compare to other altered states of consciousness (ASCs), including those mediated by certain psychedelic substances; and understand their impact on well-being. Personality trait absorption and temporal lobe lability (TLL) were assessed as predictors of Spontaneous Spiritual and Kundalini Awakenings (SSA/SKAs). A mixed within and between-participants self-report survey design was adopted. A total of 152 participants reporting their most powerful SSA/SKAs completed questionnaires measuring nondual, kundalini, and mystical experience, as well as depth of ASC, and trait absorption and TLL. Spontaneous Kundalini Awakenings were found to be significantly more physical, but not significantly more negative than SSAs, and overall, both sets of experiences were perceived to be overwhelmingly more positive than negative, even in cases where the experience was initially challenging. The phenomenological distribution of SSA/SKAs was similar to other measured ASCs although greater in magnitude, and appeared most similar in distribution and in magnitude to drug-induced ASCs, particularly classic psychedelics DMT and psilocybin. Temporal lobe lability and trait absorption were found to predict the SSA/SKA experience. The limitations and implications of these findings are discussed.

Consciousness in active inference: Deep self-models, other minds, and the challenge of psychedelic-induced ego-dissolution

Predictive processing approaches to brain function are increasingly delivering promise for illuminating the computational underpinnings of a wide range of phenomenological states. It remains unclear, however, whether predictive processing is equipped to accommodate a theory of consciousness itself. Furthermore, objectors have argued that without specification of the core computational mechanisms of consciousness, predictive processing is unable to inform the attribution of consciousness to other non-human (biological and artificial) systems. In this paper, I argue that an account of consciousness in the predictive brain is within reach via recent accounts of phenomenal self-modelling in the active inference framework. The central claim here is that phenomenal consciousness is underpinned by 'subjective valuation'-a deep inference about the precision or 'predictability' of the self-evidencing ('fitness-promoting') outcomes of action. Based on this account, I argue that this approach can critically inform the distribution of experience in other systems, paying particular attention to the complex sensory attenuation mechanisms associated with deep self-models. I then consider an objection to the account: several recent papers argue that theories of consciousness that invoke self-consciousness as constitutive or necessary for consciousness are undermined by states (or traits) of 'selflessness'; in particular the 'totally selfless' states of ego-dissolution occasioned by psychedelic drugs. Drawing on existing work that accounts for psychedelic-induced ego-dissolution in the active inference framework, I argue that these states do not threaten to undermine an active inference theory of consciousness. Instead, these accounts corroborate the view that subjective valuation is the constitutive facet of experience, and they highlight the potential of psychedelic research to inform consciousness science, computational psychiatry and computational phenomenology.

Pharmacologic Similarities and Differences Among Hallucinogens

Hallucinogens constitute a unique class of substances that cause changes in the user's thoughts, perceptions, and mood through various mechanisms of action. Although the serotonergic hallucinogens such as lysergic acid diethylamide, psilocybin, and N,N-dimethyltryptamine have been termed the classical hallucinogens, many hallucinogens elicit their actions through other mechanisms such as N-methyl-D-aspartate receptor antagonism, opioid receptor agonism, or inhibition of the reuptake of monoamines including serotonin, norepinephrine, and dopamine. The aim of this article is to compare the pharmacologic similarities and differences among substances within the hallucinogen class and their impact on physical and psychiatric effects. Potential toxicities, including life-threatening and long-term effects, will be reviewed.