Increased amygdala responses to emotional faces after psilocybin for treatment-resistant depression

The Effects of Psilocybin in Adults with Major Depressive Disorder and the General Population: Findings from Neuroimaging Studies

The use of psilocybin as treatment for major depressive disorder (MDD) has been examined as a promising alternative to traditional first-line options. We reviewed existing literature to provide a synthesis of the extant neuroimaging observations with psilocybin, and to identify putative therapeutic targets for target engagement studies with psilocybin, and potentially other psychedelics. We assessed neuroimaging observations with psilocybin among participants with MDD and healthy populations. A systematic search was conducted on PubMed, Google Scholar and PsycINFO from database inception to November 17th, 2021. The study quality (i.e., risk of bias) was assessed using the revised Cochrane risk-of-bias tool for randomized trials. A total of ten studies evaluated psilocybin in healthy populations and three studies assessed psilocybin in MDD participants using neuroimaging techniques. Following psilocybin administration, a decrease in amygdala activity and a reduction in depressive symptoms was observed in two studies. Changes in functional connectivity and activation of prefrontal limbic structures, specifically the ventral medial prefrontal cortex and amygdala, was seen in healthy populations. There was high heterogeneity in methodology (e.g., dosing schedule and imaging methods) amongst included studies. Longitudinal studies are needed to further elucidate psilocybin treatment for MDD, its long-term effects and the possibility of sustained therapeutic effects.

Don't be afraid, try to meditate- potential effects on neural activity and connectivity of psilocybin-assisted mindfulness-based intervention for social anxiety disorder: A systematic review

BACKGROUND

Current first-line treatment for social anxiety disorder (SAD), one of the most prevalent anxiety disorders, is limited in its efficacy. Hence, novel treatment approaches are urgently needed. The current review suggests a combination of meditation-based interventions and the administration of a psychedelic as a future alternative treatment approach. While both separate treatments show promise in the treatment of (other) clinical conditions, their combination has not yet been investigated in the treatment of psychopathologies.

AIM

With a systematic literature review, we aim to identify the potential mechanisms by which combined psilocybin and mindfulness treatment could adjust anomalous neural activity underlying SAD and exert therapeutic effects.

RESULTS

Thirty experimental studies investigating the neural effects of meditation or psilocybin treatment in healthy and patient samples were included. Findings suggest that psilocybin-assisted meditation interventions might change cognitive processes like biased attention to threat linked to SAD by modulating connectivity of the salience network, balancing the activity and connectivity of cortical-midline structures, and increasing frontoparietal control over amygdala reactivity.

CONCLUSIONS

Future studies should investigate whether psilocybin-assisted mindfulness-based intervention can provide therapeutic benefits to SAD patients who are do not remit following conventional therapy.

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.

Psychedelic perceptions: mental health service user attitudes to psilocybin therapy

INTRODUCTION

Despite the rapid advance of psychedelic science and possible translation of psychedelic therapy into the psychiatric clinic, very little is known about mental health service user attitudes.

OBJECTIVES

To explore mental health service user attitudes to psychedelics and psilocybin therapy.

METHODS

A questionnaire capturing demographics, diagnoses, previous psychedelic and other drug use, and attitudes to psychedelics and psilocybin therapy was distributed to mental health service users.

RESULTS

Ninety-nine participants completed the survey (52% female, mean age 42 years). The majority (72%) supported further research, with 59% supporting psilocybin as a medical treatment. A total of 27% previously used recreational psilocybin, with a male preponderance (p = 0.01). Younger age groups, those with previous psychedelic experience, and those with non-religious beliefs were more likely to have favourable attitudes towards psilocybin. A total of 55% of the total sample would accept as a treatment if doctor recommended, whereas 20% would not. Fewer people with depression/anxiety had used recreational psychedelics (p = 0.03) but were more likely to support government funded studies (p = 0.02). A minority (5%) of people with conditions (psychosis and bipolar disorder) that could be exacerbated by psilocybin thought it would be useful for them. One fifth of the total sample viewed psychedelics as addictive and unsafe even under medical supervision. Concerns included fear of adverse effects, lack of knowledge, insufficient research, illegality, and relapse if medications were discontinued.

CONCLUSIONS

The majority supported further research into psilocybin therapy. Younger people, those with previous recreational psychedelic experience, and those with non-religious beliefs were more likely to have favourable attitudes towards psilocybin therapy.

The impact of obesity-related neuroinflammation on postpartum depression: A narrative review

Obesity is currently one of the most serious health problems, affecting 13% of the world's adult population. Obesity is characterized by persistent low-grade chronic inflammation that assumes systemic proportions and triggers several associated metabolic diseases. Furthermore, obesity has been associated with an increased occurrence of central disorders such as impaired cognitive function, reward system dysfunction, and depression. In summary, there is a quantitative reduction in the release of neurotransmitters in depression. Postsynaptic cells capture lower concentrations of neurotransmitters, which leads to a functional reduction in the central nervous system (CNS). Globally, approximately 15-65% of women experience depressive symptoms during pregnancy, depending on their location. Depressive symptoms persist in some women, leading to postpartum depression (PPD). Thus, obesity may be considered a risk factor for PPD development. This study aimed to synthesize studies on the impact of obesity-related neuroinflammation and PPD. We conducted a narrative review of the relevant literature. The search was performed in electronic databases, specifically PubMed, selecting articles in English published from 2014 to 2021 using the narrative review methodology.

The psychological processes of classic psychedelics in the treatment of depression: a systematic review protocol

BACKGROUND

There is currently renewed interest in the use of psychedelic therapy in the treatment of psychiatric disorders, including depression. The proposed systematic review will aim to identify, evaluate and summarise the psychological processes of change underlying psychedelic therapy for depression in the current literature and consider the implications these processes may have on the psychotherapy component of treatment.

METHODS

Scopus, PsycINFO, PubMed and Web of Science databases will be searched using relevant terms. Studies will be included if they discuss the use of a classic psychedelic to treat depression symptomology in an adult population and report or propose psychological processes responsible for depression symptom change. Two authors will independently screen articles, complete quality assessment tools and conduct data extraction. Empirical and non-empirical research will be extracted and synthesised separately. A narrative synthesis approach will be used to report psychological processes identified in the literature.

DISCUSSION

This systematic review will be the first to collate available evidence on the psychological processes associated with psychedelic therapy for depression. The preliminary nature of this research field is expected to result in the review having several limitations, namely heterogeneity between studies and the inclusion of limited empirical research. We intend for this review to present the current state of the literature, identify gaps and generate candidate variables that warrant further investigation.

SYSTEMATIC REVIEW

PROSPERO CRD42020197202.

The Acceptance/Avoidance-Promoting Experiences Questionnaire (APEQ): A theory-based approach to psychedelic drugs' effects on psychological flexibility

BACKGROUND

Many benefits and some harms associated with psychedelic use could be attributable to these drugs' acceptance/avoidance-promoting effects and corresponding changes in psychological flexibility. Underlying psychological mechanisms are insufficiently understood.

AIM

The purpose of this study was the validation of a psychological model of acceptance/avoidance-promoting psychedelic experiences, which included the development of a theory-based self-report instrument: the Acceptance/Avoidance-Promoting Experiences Questionnaire (APEQ). Its two main scales, acceptance-related experience (ACE) and avoidance-related experience (AVE), represent the theorized model's core constructs. We aimed to test the model's central assumptions of complementarity (ACE and AVE may occur alternatingly but not simultaneously, and are therefore empirically independent), intertwinedness (subaspects within ACE and AVE are mutually contingent and therefore highly inter-correlated), context-dependence (ACE and AVE depend on context factors) and interaction (longer-term outcomes depend on the interplay between ACE and AVE).

METHOD

A bilingual retrospective online survey including 997 English- and 836 German-speaking participants. Each participant reported on one psychedelic experience occasioned by lysergic acid diethylamide (LSD), psilocybin, mescaline, or ayahuasca.

RESULTS

Whereas ACE and AVE were found to be relatively independent aspects of participants' reported psychedelic experiences (complementarity), their subaspects were mostly distinguishable but strongly correlated among each other (intertwinedness). Therapeutic, escapist, and hedonic use motives were differentially associated with ACE and AVE (context-dependence), which were in turn associated with retrospective changes in psychological flexibility following participants' reported experiences. The positive association between ACE and increased psychological flexibility was significantly moderated by AVE (interaction).

CONCLUSION

These results provide an initial validation of the APEQ and its underlying theoretical model, suggesting the two can help clarify the psychological mechanisms of psychedelic-induced benefits and harms. Both should be further investigated in prospective-longitudinal and clinical studies.

Classic Psychedelic Drugs: Update on Biological Mechanisms

Renewed interest in the effects of psychedelics in the treatment of psychiatric disorders warrants a better understanding of the neurobiological mechanisms underlying the effects of these substances. During the past two decades, state-of-the-art studies of animals and humans have yielded new important insights into the molecular, cellular, and systems-level actions of psychedelic drugs. These efforts have revealed that psychedelics affect primarily serotonergic receptor subtypes located in cortico-thalamic and cortico-cortical feedback circuits of information processing. Psychedelic drugs modulate excitatory-inhibitory balance in these circuits and can participate in neuroplasticity within brain structures critical for the integration of information relevant to sensation, cognition, emotions, and the narrative of self. Neuroimaging studies showed that characteristic dimensions of the psychedelic experience obtained through subjective questionnaires as well as alterations in self-referential processing and emotion regulation obtained through neuropsychological tasks are associated with distinct changes in brain activity and connectivity patterns at multiple-system levels. These recent results suggest that changes in self-experience, emotional processing, and social cognition may contribute to the potential therapeutic effects of psychedelics.

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.

Psychedelic-Assisted Therapy for Substance Use Disorders and Potential Mechanisms of Action

Substance use disorders (SUD) represent a significant public health issue with a high need for novel and efficacious treatment options. In light of this high unmet need, recent results reporting beneficial outcomes of psychedelic-assisted therapy in SUD are particularly relevant. However, several questions remain with regard to this treatment approach. The clinical mechanisms of action of psychedelic substances in the treatment of SUD are not well understood. Closing this knowledge gap is critical to inform and optimize the psychotherapeutic embedding of the acute substance administration. In this chapter, we discuss potential mechanisms that have implications on psychotherapeutic approaches including induced neuroplasticity, alterations in brain network connectivity, reward and emotion processing, social connectedness, insight, and mystical experiences. Furthermore, we outline considerations and approaches that leverage these mechanisms in order to optimize the therapeutic embedding by maximizing synergy between substance effects and psychotherapy. Understanding the mechanisms of action, developing psychotherapeutic approaches accordingly, and evaluating their synergistic efficacy in scientific studies will be critical to advance the framework of psychedelic-assisted therapy for addiction, create evidence-based approaches, and achieve the best treatment outcome for patients with SUD.

Reactivations after 5-methoxy-N,N-dimethyltryptamine use in naturalistic settings: An initial exploratory analysis of the phenomenon's predictors and its emotional valence

BACKGROUND

The psychedelic 5-MeO-DMT has shown clinical potential due to its short duration and ability to induce mystical experiences. However, a phenomenon known as "reactivations" (similar to "flashbacks") is a poorly understood and frequently reported phenomenon which appears associated with 5-MeO-DMT use and warranted further investigation.

AIMS

This study examined whether differences in age, gender, education, lifetime use, use location, and preparation strategies predict reactivations (primary outcome). Additionally, we explored how reactivations were perceived by survey respondents and whether demographic data predicted emotional valence (secondary outcome) of reported reactivations.

MATERIALS AND METHODS

This study used secondary quantitative data from a survey assessing epidemiological and behavioral associations of 5-MeO-DMT use in non-clinical settings (N = 513). Descriptive statistics, chi-square tests, t-tests, and logistic regressions were utilized to explore aims.

RESULTS

Being female, older at the time of first 5-MeO-DMT dose, having higher educational attainment, and dosing in a structured group setting were associated with increased odds of reporting a reactivation event. Higher mystical experience scores, greater personal wellbeing and having had a non-dual awareness experience that was not substance-induced were associated with higher likelihood of reporting a neutral or positive emotional valence of a reactivation event.

CONCLUSION

These findings suggest that reactivation phenomena, in this particular sample may most often represent a neutral or positive byproduct of the acute 5-MeO-DMT experience. More information is needed to best identify individuals most likely to experience a reactivation as a negative event to prevent such potential challenging outcomes.

Serotonergic psychedelics for depression: What do we know about neurobiological mechanisms of action?

INTRODUCTION

Current treatment options for major depressive disorder (MDD) have limited efficacy and are associated with adverse effects. Recent studies investigating the antidepressant effect of serotonergic psychedelics-also known as classic psychedelics-have promising preliminary results with large effect sizes. In this context, we conducted a review of the putative neurobiological underpinnings of the mechanism of antidepressant action of these drugs.

METHODS

A narrative review was conducted using PubMed to identify published articles evaluating the antidepressant mechanism of action of serotonergic psychedelics.

RESULTS

Serotonergic psychedelics have serotonin (5HT)2A agonist or partial agonist effects. Their rapid antidepressant effects may be mediated-in part-by their potent 5HT2A agonism, leading to rapid receptor downregulation. In addition, these psychedelics impact brain derived neurotrophic factor and immunomodulatory responses, both of which may play a role in their antidepressant effect. Several neuroimaging and neurophysiology studies evaluating mechanistic change from a network perspective can help us to further understand their mechanism of action. Some, but not all, data suggest that psychedelics may exert their effects, in part, by disrupting the activity of the default mode network, which is involved in both introspection and self-referential thinking and is over-active in MDD.

CONCLUSION

The mechanisms of action underlying the antidepressant effect of serotonergic psychedelics remains an active area of research. Several competing theories are being evaluated and more research is needed to determine which ones are supported by the most robust evidence.

Mindful nonreactivity moderates the relationship between posttraumatic stress disorder and depression

PTSD and depression represent major individual and societal burdens. Depression is commonly comorbid with PTSD among veterans, although buffers of this relationship are unclear. We evaluated whether facets of mindfulness moderated the relationship between PTSD and depression in veterans with PTSD (N = 70). Three facets - nonjudging, acting with awareness, and nonreactivity - were assessed as moderators. Results indicated nonreactivity significantly attenuated the relationship between PTSD and depression (p=.013), such that veterans with high nonreactivity (+1 SD) showed a nonsignificant relationship between PTSD and depression, whereas veterans with average (Mean; p<.001) and low (-1 SD; p<.001) nonreactivity exhibited a significant relationship.

Neuroimaging Correlates of Treatment Response with Psychedelics in Major Depressive Disorder: A Systematic Review

Preliminary evidence supports the use of psychedelics for major depressive disorder (MDD). However, less attention has been given to the neural mechanisms behind their effects. We conducted a systematic review examining the neuroimaging correlates of antidepressant response following psychedelic interventions for MDD. Through MEDLINE, Embase, and APA PsycINFO, 187 records were identified and 42 articles were screened. Six published studies and one conference abstract were included. Five ongoing trials were included from subjective outcomesTrials.gov. Our search covered several psychedelics, though included studies were specific to psilocybin, ayahuasca, and lysergic acid diethylamide. Three psilocybin studies noted amygdala activity and functional connectivity (FC) alterations that correlated with treatment response. Two psilocybin studies reported that FC changes in the medial and ventromedial prefrontal cortices correlated with treatment response. Two trials from a single study reported global decreases in brain network modularity which correlated with antidepressant response. One ayahuasca study reported increased activity in the limbic regions following treatment. Preliminary evidence suggests that the default mode and limbic networks may be a target for future research on the neural mechanisms of psychedelics. More data is required to corroborate these initial findings as the evidence summarized in this review is based on four datasets.

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.

1H Nuclear Magnetic Resonance: A Future Approach to the Metabolic Profiling of Psychedelics in Human Biofluids?

While psychedelics may have therapeutic potential for treating mental health disorders such as depression, further research is needed to better understand their biological effects and mechanisms of action when considering the development of future novel therapy approaches. Psychedelic research could potentially benefit from the integration of metabonomics by proton nuclear magnetic resonance (1H NMR) spectroscopy which is an analytical chemistry-based approach that can measure the breakdown of drugs into their metabolites and their metabolic consequences from various biofluids. We have performed a systematic review with the primary aim of exploring published literature where 1H NMR analysed psychedelic substances including psilocin, lysergic acid diethylamide (LSD), LSD derivatives, N,N-dimethyltryptamine (DMT), 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT) and bufotenin. The second aim was to assess the benefits and limitations of 1H NMR spectroscopy-based metabolomics as a tool in psychedelic research and the final aim was to explore potential future directions. We found that the most current use of 1H NMR in psychedelic research has been for the structural elucidation and analytical characterisation of psychedelic molecules and that no papers used 1H NMR in the metabolic profiling of biofluids, thus exposing a current research gap and the underuse of 1H NMR. The efficacy of 1H NMR spectroscopy was also compared to mass spectrometry, where both metabonomics techniques have previously shown to be appropriate for biofluid analysis in other applications. Additionally, potential future directions for psychedelic research were identified as real-time NMR, in vivo 1H nuclear magnetic resonance spectroscopy (MRS) and 1H NMR studies of the gut microbiome. Further psychedelic studies need to be conducted that incorporate the use of 1H NMR spectroscopy in the analysis of metabolites both in the peripheral biofluids and in vivo to determine whether it will be an effective future approach for clinical and naturalistic research.

Medicinal psychedelics for mental health and addiction: Advancing research of an emerging paradigm

The medical use of psychedelic substances (e.g. psilocybin, ayahuasca, lysergic acid diethylamide and 3,4-methylenedioxymethamphetamine) is attracting renewed interest, driven by a pressing need for research and development of novel therapies for psychiatric disorders, as well as promising results of contemporary studies. In this Viewpoint, we reflect upon the 'Clinical Memorandum on Psychedelics' recently released by the Royal Australian and New Zealand College of Psychiatrists and note subsequent developments including the application for down-scheduling of psilocybin and 3,4-methylenedioxymethamphetamine presently being considered by the Therapeutic Goods Administration and approvals for access via the Special Access Scheme. We suggest that this field is worthy of rigorous research to assess potential benefits, address safety parameters and clarify therapeutic mechanisms. To this end, we outline recent research findings, provide an overview of current knowledge relating to mechanisms of action and discuss salient aspects of the psychedelic-assisted psychotherapy treatment model. The sum of this research points towards medicinal psychedelics as a potential new class of psychiatric treatments when used within a medically supervised framework with integrated psychotherapeutic support. However, before widespread translation into clinical use can occur, appropriately designed and sufficiently powered trials are required to detect both potential positive and negative outcomes. Unique safety and regulatory challenges also need to be addressed. As for any new medical therapy, psychedelic research needs to be conducted in a rigorous manner, through the dispassionate lens of scientific enquiry. Carte blanche availability to practitioners, without specific protocols and appropriate training, would be potentially harmful to individuals and detrimental to the field.

Examining Psychedelic-Induced Changes in Social Functioning and Connectedness in a Naturalistic Online Sample Using the Five-Factor Model of Personality

The present study examines prospective changes in personality traits relevant to social functioning as well as perceived social connectedness in relation to the naturalistic use of psychedelic compounds in an online volunteer sample. The study also examined the degree to which demographic characteristics, social setting, baseline personality, and acute subjective factors (e.g., emotional breakthrough experiences) influenced trajectories of personality and perceived social connectedness. Participants recruited online completed self-report measures of personality and social connectedness at three timepoints (baseline, 2weeks post-experience, 4weeks post-experience). Linear mixed models were used to examine changes in outcomes and the moderation of these outcomes by covariates. The most substantive changes were reductions in the personality domains Neuroticism, and increases in Agreeableness and social connectedness. Notably, reductions in Neuroticism and increases in Agreeableness covaried over time, which may be suggestive of common processes involving emotion regulation. Preliminary evidence was found for a specific effect on a component of Agreeableness involving a critical and quarrelsome interpersonal style. Although moderation by demographic characteristics, social setting, baseline personality, and acute factors generally found limited support, baseline standing on Neuroticism, perspective taking, and social connectedness showed tentative signs of amplifying adaptive effects on each trait, respectively. Our findings hold implications for the potential use of psychedelics for treating interpersonal elements of personality pathology as well as loneliness.

Ayahuasca for the Treatment of Depression

Ayahuasca, the vine of the souls in Quechua, is a psychedelic brew with a few formulations that most often include the bark of a liana in the Malpighiaceae family (Banisteriopsis caapi), with leaves from a shrub in the coffee family Rubiaceae (Psychotria viridis). Mixed with water and boiled for hours or days, it produces a brownish-colored liquid with a strong and characteristic taste. Ayahuasca contains the psychedelic tryptamine N,N-Dimethyltryptamine (DMT), and Monoamine Oxidase Inhibitors (MAOi), and in the past few years, it has been tested. In recent years its antidepressant properties have been put to the test. Evidence from open and randomized placebo-controlled clinical trials has shown encouraging results, indicating significant and rapid antidepressant effects, starting as early as 1 day after the ayahuasca intervention. In addition, we have explored the nature of these effects using multivariate measures. In this article, we will review the history, pharmacology, clinical trials, and clinical and behavioral markers associated with the antidepressant effects of ayahuasca.

The Effects of Tryptamine Psychedelics in the Brain: A meta-Analysis of Functional and Review of Molecular Imaging Studies

There is an increasing interest in the neural effects of psychoactive drugs, in particular tryptamine psychedelics, which has been incremented by the proposal that they have potential therapeutic benefits, based on their molecular mimicry of serotonin. It is widely believed that they act mainly through 5HT2A receptors but their effects on neural activation of distinct brain systems are not fully understood. We performed a quantitative meta-analysis of brain imaging studies to investigate the effects of substances within this class (e.g., LSD, Psilocybin, DMT, Ayahuasca) in the brain from a molecular and functional point of view. We investigated the question whether the changes in activation patterns and connectivity map into regions with larger 5HT1A/5HT2A receptor binding, as expected from indolaemine hallucinogens (in spite of the often reported emphasis only on 5HT2AR). We did indeed find that regions with changed connectivity and/or activation patterns match regions with high density of 5HT2A receptors, namely visual BA19, visual fusiform regions in BA37, dorsal anterior and posterior cingulate cortex, medial prefrontal cortex, and regions involved in theory of mind such as the surpramarginal gyrus, and temporal cortex (rich in 5HT1A receptors). However, we also found relevant patterns in other brain regions such as dorsolateral prefrontal cortex. Moreover, many of the above-mentioned regions also have a significant density of both 5HT1A/5HT2A receptors, and available PET studies on the effects of psychedelics on receptor occupancy are still quite scarce, precluding a metanalytic approach. Finally, we found a robust neuromodulatory effect in the right amygdala. In sum, the available evidence points towards strong neuromodulatory effects of tryptamine psychedelics in key brain regions involved in mental imagery, theory of mind and affective regulation, pointing to potential therapeutic applications of this class of substances.

Rediscovering Psilocybin as an Antidepressive Treatment Strategy

There has recently been a renewal of interest in psychedelic research on the use of psilocybin in psychiatric treatment and, in particular, for the treatment of major depressive disorder (MDD). Several state-of-the-art studies have provided new insight into the mechanisms of action of psilocybin and its therapeutic potential. Nevertheless, many questions remain unanswered. With this review, we provide an overview of the current state of research on the potential mechanisms of psilocybin, its antidepressant potential, and the associated risks and adverse effects, to provide an update on a controversial topic discussed in psychopharmacology. A database search was conducted in Medline including articles on psilocybin over the period of the last 20 years. Despite the promising progress in understanding the mechanisms of psilocybin, the exact antidepressive mechanism and the role of the psychedelic experience remain elusive. The studies included in this review found high treatment effect sizes for psilocybin as an antidepressant. However, the results must be regarded as preliminary due to several limitations. Although the current studies observed no severe adverse events, several questions regarding safety and utility remain and must be subject of future research.

Psychedelics and Consciousness: Distinctions, Demarcations, and Opportunities

Psychedelic substances produce unusual and compelling changes in conscious experience that have prompted some to propose that psychedelics may provide unique insights explaining the nature of consciousness. At present, psychedelics, like other current scientific tools and methods, seem unlikely to provide information relevant to the so-called "hard problem of consciousness," which involves explaining how first-person experience can emerge. However, psychedelics bear on multiple "easy problems of consciousness," which involve relations between subjectivity, brain function, and behavior. In this review, we discuss common meanings of the term "consciousness" when used with regard to psychedelics and consider some models of the effects of psychedelics on the brain that have also been associated with explanatory claims about consciousness. We conclude by calling for epistemic humility regarding the potential for psychedelic research to aid in explaining the hard problem of consciousness while pointing to ways in which psychedelics may advance the study of many specific aspects of consciousness.

The Potential Role of Serotonergic Hallucinogens in Depression Treatment

Due to an increasing number of depression diagnoses and limited effective treatments, researchers continue to explore novel therapeutic strategies for this disorder. Recently, interest has revolved around the use of serotonergic psychedelics to reduce the symptoms of depression. In this systematic review, we summarize the currently available knowledge on the safety and efficacy of psychedelic substances for the treatment of depression. A literature search of the PubMed/MEDLINE database identified 14 clinical trials from the last 10 years that examined the use of psilocybin, MDMA, DMT, or LSD for the treatment of depression symptoms. Some psychedelics, especially psilocybin, demonstrated an ability to reduce depressive symptoms as measured by several psychological scales, which was often sustained for months after the last psychedelic session. Moreover, one study revealed that psilocybin has comparable efficacy to escitalopram in the treatment of depression. None of the studies reported any serious adverse events associated with psychedelic administration. The reviewed studies suggest that psychedelics have great potential in depression therapy and, after addressing and overcoming the current study limitations, may be used as a novel method of treating depression in the future.

Cultivating Positive Health, Learning, and Community: The Return of Mesoamerica’s Quetzalcoatl and the Venus Star

For more than 3500 years, since Olmec times (1500–400 BC), the peoples of Mesoamerica have shared with one another a profound way of living involving a deep understanding of the human body and of land and cosmology. As it stands, healing ways of knowing that depend on medicinal plants, the Earth’s elements, and knowledge of the stars are still intact. The Indigenous Xicana/o/xs who belong to many of the mobile tribes of Mesoamerica share a long genealogical history of cultivating and sustaining their Native American rituals, which was weakened in Mexico and the United States during various periods of colonization. This special edition essay sheds light on the story of Quetzalcoatl and the Venus Star as a familial place of Xicana/o/x belonging and practice. To do so, we rely on the archaeological interpretation of these two entities as one may get to know them through artifacts, monuments, and ethnographic accounts, of which some date to Mesoamerica’s Formative period (1500–400 BC). Throughout this paper, ancestral medicine ways are shown to help cultivate positive health, learning, and community. Such cosmic knowledge is poorly understood, yet it may further culturally relevant education and the treatment of the rampant health disparities in communities of Mesoamerican ancestry living in the United States. The values of and insights into Indigenous Xicana/o/x knowledge and identity conclude this essay.

Psilocybin and MDMA for the treatment of trauma-related psychopathology

This review examines the role of trauma in psychiatric morbidity and analogous psychoneurobiological changes. Trauma is a necessary criterion for Post-Traumatic Stress Disorder (PTSD), however, trauma history is highly correlated with a variety of psychiatric conditions. Some evidence suggests that Major Depressive Disorder (MDD) is the most common psychiatric condition that arises following trauma. Approximately 50% of PTSD cases present with co-morbid MDD. Overlapping symptomatology and neurobiology between these conditions underlie the debate over whether these phenomena result from problematic nosology or whether comorbid MDD + PTSD is a distinct phenotype of trauma-related psychopathology. Regardless, similar treatment approaches have been employed historically, with varying success. The drug-assisted psychotherapy treatment model, which combines pharmacological and psychotherapeutic approaches, is currently being trialled as a novel treatment approach in psychiatry. Both psilocybin- and 3,4-Methylenedioxymethamphetamine (MDMA)-assisted psychotherapy have received Food and Drug Administration 'breakthrough therapy' designation for the treatment of resistant MDD and PTSD, respectively. This paper reviews the therapeutic rationale of both psilocybin and MDMA for treating both trauma-related MDD and PTSD.

Effects of Ayahuasca on the Recognition of Facial Expressions of Emotions in Naive Healthy Volunteers: A Pilot, Proof-of-Concept, Randomized Controlled Trial

BACKGROUND

The recognition of emotions in facial expressions (REFE) is a core aspect of social cognition. Previous studies with the serotonergic hallucinogens lysergic acid diethylamide and psilocybin showed that these drugs reduced the recognition of negative (fear) faces in healthy volunteers. This trial assessed the acute and prolonged effects of a single dose of ayahuasca on the REFE.

METHODS

Twenty-two healthy volunteers participated in a pilot, proof-of-concept, randomized trial. Study variables included a REFE task performed before and 4 hours after drug intake, subjective effects (self-reports/observer impressions), tolerability measures (cardiovascular measures, self-reports), and brain-derived neurotrophic factor plasma levels. The REFE task was applied again 1, 7, 14, and 21 days and 3 months after drug intake. Stability of ayahuasca alkaloids during the study was also assessed (room temperature, 18 months).

FINDINGS

Compared with placebo, ayahuasca did not modify the REFE. No significant effects were observed on cardiovascular measures and brain-derived neurotrophic factor levels. Volunteers reported visual effects, tranquility/relaxation, and well-being, with few reports of transient anxiety/confusion. Ayahuasca was well tolerated, producing mainly nausea, gastrointestinal discomfort, and vomiting. A significant time-dependent deterioration of alkaloids was observed, especially for dimethyltryptamine.

CONCLUSIONS

Absence of significant effects on the REFE task could be due to lack of effects of ayahuasca (at the doses used), alkaloid degradation, learning effects, and the high educational level of the sample. Further trials with different samples are needed to better understand the effects of ayahuasca and other serotonergic hallucinogens on the REFE. Future trials should improve methods to guarantee the stability of ayahuasca alkaloids.

Clinical and biological predictors of psychedelic response in the treatment of psychiatric and addictive disorders: A systematic review

BACKGROUND

The use of psychedelic treatments has shown very promising results in some psychiatric and addictive disorders, but not all patients achieved a response.

AIM

The aim of this review is to explore the clinical and biological factors which could predict the response to psychedelics in psychiatric and addictive disorders.

METHODS

A systematic research was performed on MEDLINE, PsycInfo, Web of science, and Scopus databases from January 1990 to May 2020. All studies investigating the predictive factors of response to psychedelics regardless of psychiatric or addictive disorders, were included.

RESULTS

Twenty studies investigating addictive disorder, treatment-resistant depression, obsessive-compulsive disorder and depressive and anxiety symptoms in patients with life-threatening cancer were included in this review. We found that, in all indications, the main predictive factor of response to psychedelics is the intensity of the acute psychedelic experience. Indeed, we found this factor for alcohol and tobacco use disorders, treatment-resistant depression, and anxiety and depressive symptoms in patients with life-threatening cancer, but not for obsessive-compulsive disorder.

CONCLUSION

The intensity of the acute psychedelic experience was the main predicting factor of response. The action mechanism of this experience was not clear, but some hypotheses could be made, such as a modulation of serotoninergic system by 5-HT2A receptors agonism, a modulation of the default mode network (DMN) with an acute modular disintegration of the DMN followed by a re-integration of this network with a normal functioning, or an anti-inflammatory effect of this treatment.

Hallucinogenic/psychedelic 5HT2A receptor agonists as rapid antidepressant therapeutics: Evidence and mechanisms of action

Major depressive disorder (MDD) is among the most prevalent mental health disorders worldwide, and it is associated with a reduced quality of life and enormous costs to health care systems. Available drug treatments show low-to-moderate response in most patients, with almost a third of patients being non-responders (treatment-resistant). Furthermore, most currently available medications need several weeks to achieve therapeutic effects, and the long-term use of these drugs is often associated with significant unwanted side effects and resultant reductions in treatment compliance. Therefore, more effective, safer, and faster-acting antidepressants with enduring effects are needed. Together with ketamine, psychedelics (or classic or serotoninergic hallucinogens) such as lysergic acid diethylamide (LSD), psilocybin, and ayahuasca are among the few compounds with recent human evidence of fast-acting antidepressant effects. Several studies in the 1950s to 1970s reported antidepressive and anxiolytic effects of these drugs, which are being confirmed by modern trials (LSD, one trial; psilocybin, five trials; ayahuasca, two trials). The effects of these drugs appear to be produced primarily by their agonism at serotonin (5-hydroxytryptamine, 5-HT) receptors, especially the 5-HT_2A receptor. Considering the overall burden of MDD and the necessity of new therapeutic options, the promising (but currently limited) evidence of safety and efficacy of psychedelics has encouraged the scientific community to explore more fully their beneficial effects in MDD.

Hallucinogens in Mental Health: Preclinical and Clinical Studies on LSD, Psilocybin, MDMA, and Ketamine

A revamped interest in the study of hallucinogens has recently emerged, especially with regard to their potential application in the treatment of psychiatric disorders. In the last decade, a plethora of preclinical and clinical studies have confirmed the efficacy of ketamine in the treatment of depression. More recently, emerging evidence has pointed out the potential therapeutic properties of psilocybin and LSD, as well as their ability to modulate functional brain connectivity. Moreover, MDMA, a compound belonging to the family of entactogens, has been demonstrated to be useful to treat post-traumatic stress disorders. In this review, the pharmacology of hallucinogenic compounds is summarized by underscoring the differences between psychedelic and nonpsychedelic hallucinogens as well as entactogens, and their behavioral effects in both animals and humans are described. Together, these data substantiate the potentials of these compounds in treating mental diseases.

Increased sensitivity to strong perturbations in a whole-brain model of LSD

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Novel offline perturbational method applied on functional magnetic resonance imaging (fMRI) data under the effect of lysergic acid diethylamide (LSD).

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Shift of brain's global working point to more complex dynamics after LSD intake.

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Consistently longer recovery time after model perturbation under LSD influence.

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Strongest effects in resting state networks relevant for psychedelic experience.

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Higher response diversity across brain regions under LSD influence after an external in silico perturbation.

Lysergic acid diethylamide (LSD) is a potent psychedelic drug, which has seen a revival in clinical and pharmacological research within recent years. Human neuroimaging studies have shown fundamental changes in brain-wide functional connectivity and an expansion of dynamical brain states, thus raising the question about a mechanistic explanation of the dynamics underlying these alterations. Here, we applied a novel perturbational approach based on a whole-brain computational model, which opens up the possibility to externally perturb different brain regions in silico and investigate differences in dynamical stability of different brain states, i.e. the dynamical response of a certain brain region to an external perturbation. After adjusting the whole-brain model parameters to reflect the dynamics of functional magnetic resonance imaging (fMRI) BOLD signals recorded under the influence of LSD or placebo, perturbations of different brain areas were simulated by either promoting or disrupting synchronization in the regarding brain region. After perturbation offset, we quantified the recovery characteristics of the brain area to its basal dynamical state with the Perturbational Integration Latency Index (PILI) and used this measure to distinguish between the two brain states. We found significant changes in dynamical complexity with consistently higher PILI values after LSD intake on a global level, which indicates a shift of the brain's global working point further away from a stable equilibrium as compared to normal conditions. On a local level, we found that the largest differences were measured within the limbic network, the visual network and the default mode network. Additionally, we found a higher variability of PILI values across different brain regions after LSD intake, indicating higher response diversity under LSD after an external perturbation. Our results provide important new insights into the brain-wide dynamical changes underlying the psychedelic state - here provoked by LSD intake - and underline possible future clinical applications of psychedelic drugs in particular psychiatric disorders.

Classical Psychedelics as Therapeutics in Psychiatry - Current Clinical Evidence and Potential Therapeutic Mechanisms in Substance Use and Mood Disorders

Classical psychedelics, primarily psilocybin and lysergic acid diethylamide (LSD), have been used and extensively studied in Western medicine as part of substance-assisted psychotherapy in the 1950s and 1960s. Modern clinical research is currently gaining momentum and provides new evidence for the safety and efficacy of classical psychedelics (primarily psilocybin, but also LSD and ayahuasca) in the treatment of different psychiatric conditions, including substance use and mood disorders.In this review article, we outline common pathological mechanisms of substance use disorders (SUD) and unipolar depression. Next, the current literature on the effects of psychedelics is summarized in order to generate hypotheses regarding their potential therapeutic mechanisms of action in treating these psychiatric conditions. Finally, we review and discuss clinical trials published since 2011 investigating the effects of psychedelics in SUD and depression.While results from those modern clinical trials are promising, most of them do not meet the methodological requirements to allow firm conclusions on the clinical efficacy of psychedelics. Larger, blinded, randomized controlled trials (RCT) with clearly defined patient groups and well-defined primary endpoints are needed. Additionally, the therapeutic mechanisms of classical psychedelics are currently unknown. This review presents hypotheses derived from preclinical and human studies that need to be tested in future trials to better understand the clinical potential of psychedelic substances in modern psychiatry.

A continuum hypothesis of psychotomimetic rapid antidepressants

Ketamine, classical psychedelics and sleep deprivation are associated with rapid effects on depression. Interestingly, these interventions also have common psychotomimetic actions, mirroring aspects of psychosis such as an altered sense of self, perceptual distortions and distorted thinking. This raises the question whether these interventions might be acute antidepressants through the same mechanisms that underlie some of their psychotomimetic effects. That is, perhaps some symptoms of depression can be understood as occupying the opposite end of a spectrum where elements of psychosis can be found on the other side. This review aims at reviewing the evidence underlying a proposed continuum hypothesis of psychotomimetic rapid antidepressants, suggesting that a range of psychotomimetic interventions are also acute antidepressants as well as trying to explain these common features in a hierarchical predictive coding framework, where we hypothesise that these interventions share a common mechanism by increasing the flexibility of prior expectations. Neurobiological mechanisms at play and the role of different neuromodulatory systems affected by these interventions and their role in controlling the precision of prior expectations and new sensory evidence will be reviewed. The proposed hypothesis will also be discussed in relation to other existing theories of antidepressants. We also suggest a number of novel experiments to test the hypothesis and highlight research areas that could provide further insights, in the hope to better understand the acute antidepressant properties of these interventions.

Using Psychedelics With Therapeutic Intent Is Associated With Lower Shame and Complex Trauma Symptoms in Adults With Histories of Child Maltreatment

BACKGROUND

Child maltreatment negatively affects the formation of internal schemata of self and other during development, leading to negative adaptations in self-concept and social cognition. Clinical reports suggest the efficacy of psychedelics in treating the psychopathological sequelae of child maltreatment. Altering maladaptive schemata of self and other implicated in negative self-concept and impaired social cognition may be a central mechanism for reducing posttraumatic stress symptoms.

AIMS

This study aims to assess whether psychedelic use moderates the relationships between child maltreatment and self-concept, social cognition, and posttraumatic stress symptoms.

METHOD

An online survey was completed by 166 participants and included measures of maltreatment exposure and severity, history of intentional therapeutic psychedelic use, posttraumatic stress symptoms, internalized shame, and facial emotion recognition.

RESULTS

Child maltreatment significantly correlated with posttraumatic stress symptoms (r = .26 and r = .20, p < .01) and internalized shame (r = .18, p < .05). Of all maltreatment subtypes, emotional abuse and neglect most strongly correlated with complex trauma symptoms (r = .32, p < .001) and internalized shame (r = .31, p < .001). Participants with a history of intentional therapeutic psychedelic use reported significantly lower complex trauma symptoms (d = 0.33, p < .05) and internalized shame (d = 0.35, p < .05) despite similar histories of maltreatment. Differences in complex trauma symptoms (d = 0.66, p < .01) and internalized shame (d = 0.80, p < .001) were largest for participants with a history of more than 5 occasions of intentional therapeutic psychedelic use. A history of more than 5 occasions of intentional therapeutic psychedelic use significantly moderated the relationship between emotional abuse and neglect and complex trauma symptoms (p < .01). No associations were found between maltreatment or psychedelic use and facial emotion recognition.

CONCLUSION

These findings demonstrate that using psychedelic drugs with therapeutic intent is associated with lower levels of complex trauma symptoms and internalized shame in individuals with histories of child maltreatment. Psychedelic use may have therapeutic benefit in treating the posttraumatic sequelae of child maltreatment.

Psychedelics in Psychiatry: Neuroplastic, Immunomodulatory, and Neurotransmitter Mechanisms

Mounting evidence suggests safety and efficacy of psychedelic compounds as potential novel therapeutics in psychiatry. Ketamine has been approved by the Food and Drug Administration in a new class of antidepressants, and 3,4-methylenedioxymethamphetamine (MDMA) is undergoing phase III clinical trials for post-traumatic stress disorder. Psilocybin and lysergic acid diethylamide (LSD) are being investigated in several phase II and phase I clinical trials. Hence, the concept of psychedelics as therapeutics may be incorporated into modern society. Here, we discuss the main known neurobiological therapeutic mechanisms of psychedelics, which are thought to be mediated by the effects of these compounds on the serotonergic (via 5-HT_2A and 5-HT_1A receptors) and glutamatergic [via N-methyl-d-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors] systems. We focus on 1) neuroplasticity mediated by the modulation of mammalian target of rapamycin-, brain-derived neurotrophic factor-, and early growth response-related pathways; 2) immunomodulation via effects on the hypothalamic-pituitary-adrenal axis, nuclear factor ĸB, and cytokines such as tumor necrosis factor-α and interleukin 1, 6, and 10 production and release; and 3) modulation of serotonergic, dopaminergic, glutamatergic, GABAergic, and norepinephrinergic receptors, transporters, and turnover systems. We discuss arising concerns and ways to assess potential neurobiological changes, dependence, and immunosuppression. Although larger cohorts are required to corroborate preliminary findings, the results obtained so far are promising and represent a critical opportunity for improvement of pharmacotherapies in psychiatry, an area that has seen limited therapeutic advancement in the last 20 years. Studies are underway that are trying to decouple the psychedelic effects from the therapeutic effects of these compounds. SIGNIFICANCE STATEMENT: Psychedelic compounds are emerging as potential novel therapeutics in psychiatry. However, understanding of molecular mechanisms mediating improvement remains limited. This paper reviews the available evidence concerning the effects of psychedelic compounds on pathways that modulate neuroplasticity, immunity, and neurotransmitter systems. This work aims to be a reference for psychiatrists who may soon be faced with the possibility of prescribing psychedelic compounds as medications, helping them assess which compound(s) and regimen could be most useful for decreasing specific psychiatric symptoms.

Psychedelic Psychiatry's Brave New World

After a legally mandated, decades-long global arrest of research on psychedelic drugs, investigation of psychedelics in the context of psychiatric disorders is yielding exciting results. Outcomes of neuroscience and clinical research into 5-Hydroxytryptamine 2A (5-HT2A) receptor agonists, such as psilocybin, show promise for addressing a range of serious disorders, including depression and addiction.

Psychedelic drugs: neurobiology and potential for treatment of psychiatric disorders

Renewed interest in the use of psychedelics in the treatment of psychiatric disorders warrants a better understanding of the neurobiological mechanisms underlying the effects of these substances. After a hiatus of about 50 years, state-of-the art studies have recently begun to close important knowledge gaps by elucidating the mechanisms of action of psychedelics with regard to their effects on receptor subsystems, systems-level brain activity and connectivity, and cognitive and emotional processing. In addition, functional studies have shown that changes in self-experience, emotional processing and social cognition may contribute to the potential therapeutic effects of psychedelics. These discoveries provide a scientific road map for the investigation and application of psychedelic substances in psychiatry.

Psychedelic science in post-COVID-19 psychiatry

The medium- to long-term consequences of COVID-19 are not yet known, though an increase in mental health problems are predicted. Multidisciplinary strategies across socio-economic and psychological levels may be needed to mitigate the mental health burden of COVID-19. Preliminary evidence from the rapidly progressing field of psychedelic science shows that psilocybin therapy offers a promising transdiagnostic treatment strategy for a range of disorders with restricted and maladaptive habitual patterns of cognition and behaviour, notably depression, addiction and obsessive compulsive disorder. The COMPASS Pathways (COMPASS) phase 2b double-blind trial of psilocybin therapy in antidepressant-free, treatment-resistant depression (TRD) is underway to determine the safety, efficacy and optimal dose of psilocybin. Results from the Imperial College London Psilodep-RCT comparing the efficacy and mechanisms of action of psilocybin therapy to the selective serotonin reuptake inhibitor (SSRI) escitalopram will soon be published. However, the efficacy and safety of psilocybin therapy in conjunction with SSRIs in TRD is not yet known. An additional COMPASS study, with a centre in Dublin, will begin to address this question, with potential implications for the future delivery of psilocybin therapy. While at a relatively early stage of clinical development, and notwithstanding the immense challenges of COVID-19, psilocybin therapy has the potential to play an important therapeutic role for various psychiatric disorders in post-COVID-19 clinical psychiatry.

Psychedelics and virtual reality: parallels and applications

Psychedelic drugs and virtual reality (VR) each have the capacity to disrupt the rigidity and limitations of typical conscious experience. This article delineates the parallels among psychedelic and VR states as well as their potential synergistic applications in clinical and recreational settings. Findings indicate that, individually, psychedelics and VR are used in analogous ways to alter sensory experience and evoke awe. They are also both used in tandem with traditional therapies to treat a variety of mood disorders; their shared capacity to transiently alter perspective and disrupt rigid patterns of mental experience may underly their analogous and transdiagnostic therapeutic uses. In terms of their combined applications, a number of recreational users currently utilize psychedelics and VR together to enhance their experience. We propose that VR may be a useful tool for preparing hallucinogen-naïve participants in clinical trials for the sensory distortions experienced in psychedelic states. Given the critical role of "setting" in psychedelic treatment outcomes, we also detail how VR could be used to optimize the environment in psychedelic sessions. Finally, we provide considerations for future studies and detail how advancements in psychedelic and VR research can inform one another. Collectively, this article outlines a number of connections between psychedelics and VR, and, more broadly, is representative of growing scientific interest into the interactions among technology, psychopharmacology, and mental health.

Post-Psychedelic Reductions in Experiential Avoidance Are Associated With Decreases in Depression Severity and Suicidal Ideation

Psychedelic therapy shows promise as a novel intervention for a wide range of mental health concerns but its therapeutic action is incompletely understood. In line with acceptance and commitment therapy's (ACT's) transdiagnostic model, qualitative research has suggested that reductions in experiential avoidance are an important component of therapeutic outcomes associated with psychedelics. However, limited research has quantitatively explored the association between decreases in experiential avoidance and therapeutic outcomes associated with psychedelics. Therefore, in two prospective studies, using convenience samples of individuals with plans to use a psychedelic, we explored the impact of psychedelic use on experiential avoidance, depression severity, and suicidal ideation, as well as relationships between changes in these outcomes. Participants (Study 1, N=104; Study 2, N=254) completed self-report questionnaires of depression severity, suicidal ideation, and experiential avoidance: 1) before using a psychedelic (in ceremonial and non-ceremonial contexts), as well as 2) 2-weeks and 3) 4-weeks after psychedelic use. Across both studies, repeated measures ANOVAs indicated significant decreases in experiential avoidance, depression severity, and suicidal ideation after psychedelic use. Furthermore, decreases in experiential avoidance were significantly associated with decreases in depression severity and suicidal ideation. These results suggest that psychedelics may lead to significant decreases in experiential avoidance, depression severity, and suicidal ideation. Additionally, these findings imply that reduced experiential avoidance may be a transdiagnostic mechanism mediating treatment success within psychedelic therapy. We conclude that integrating psychedelics with psychotherapeutic interventions that target experiential avoidance (e.g. ACT) may enhance therapeutic outcomes.

Preliminary Report on the Effects of a Low Dose of LSD on Resting-State Amygdala Functional Connectivity

BACKGROUND

The practice of "microdosing," or the use of repeated, very low doses of lysergic acid diethylamide (LSD) to improve mood or cognition, has received considerable public attention, but empirical studies are lacking. Controlled studies are needed to investigate both the therapeutic potential and the neurobiological underpinnings of this pharmacologic treatment.

METHODS

The present study was designed to examine the effects of a single low dose of LSD (13 μg) versus placebo on resting-state functional connectivity and cerebral blood flow in healthy young adults. Twenty men and women, 18 to 35 years old, participated in 2 functional magnetic resonance imaging scanning sessions in which they received placebo or LSD under double-blind conditions. During each session, the participants completed drug effect and mood questionnaires, and physiological measures were recorded. During expected peak drug effect, they underwent resting-state blood oxygen level-dependent and arterial spin labeling scans. Cerebral blood flow as well as amygdala and thalamic connectivity were analyzed.

RESULTS

LSD increased amygdala seed-based connectivity with the right angular gyrus, right middle frontal gyrus, and the cerebellum, and decreased amygdala connectivity with the left and right postcentral gyrus and the superior temporal gyrus. This low dose of LSD had weak and variable effects on mood, but its effects on positive mood were positively correlated with the increase in amygdala-middle frontal gyrus connectivity strength.

CONCLUSIONS

These preliminary findings show that a very low dose of LSD, which produces negligible subjective changes, alters brain connectivity in limbic circuits. Additional studies, especially with repeated dosing, will reveal whether these neural changes are related to the drug's purported antidepressant effect.

Depression, Mindfulness, and Psilocybin: Possible Complementary Effects of Mindfulness Meditation and Psilocybin in the Treatment of Depression. A Review

Depression is a major public health problem that affects approximately 4.4% of the global population. Since conventional pharmacotherapies and psychotherapies are only partially effective, as demonstrated by the number of patients failing to achieve remission, alternative treatments are needed. Mindfulness meditation (MM) and psilocybin represent two promising novel treatments that might even have complementary therapeutic effects when combined. Since the current literature is limited to theoretical and empirical underpinnings of either treatment alone, the present review aimed to identify possible complementary effects that may be relevant to the treatment of depression. To that end, the individual effects of MM and psilocybin, and their underlying working mechanisms, were compared on a non-exhaustive selection of six prominent psychological and biological processes that are well known to show impairments in patients suffering from major depression disorder, that is mood, executive functioning, social skills, neuroplasticity, core neural networks, and neuroendocrine and neuroimmunological levels. Based on predefined search strings used in two online databases (PubMed and Google Scholar) 1129 articles were identified. After screening title and abstract for relevance related to the question, 82 articles were retained and 11 were added after reference list search, resulting in 93 articles included in the review. Findings show that MM and psilocybin exert similar effects on mood, social skills, and neuroplasticity; different effects were found on executive functioning, neural core networks, and neuroendocrine and neuroimmune system markers. Potential mechanisms of MM's effects are enhanced affective self-regulation through mental strategies, optimization of stress reactivity, and structural and functional adjustments of prefrontal and limbic areas; psilocybin's effects might be established via attenuation of cognitive associations through deep personal insights, cognitive disinhibition, and global neural network disintegration. It is suggested that, when used in combination, MM and psilocybin could exert complementary effects by potentiating or prolonging mutual positive effects, for example, MM potentially facilitating psilocybin-induced peak experiences. Future placebo-controlled double-blind randomized trials focusing on psilocybin-assisted mindfulness-based therapy will provide knowledge about whether the proposed combination of therapies maximizes their efficacy in the treatment of depression or depressive symptomatology.

Long-term effects of psychedelic drugs: A systematic review

Research into the basic effects and therapeutic applications of psychedelic drugs has grown considerably in recent years. Yet, pressing questions remain regarding the substances' lasting effects. Although individual studies have begun monitoring sustained changes, no study to-date has synthesized this information. Therefore, this systematic review aims to fill this important gap in the literature by synthesizing results from 34 contemporary experimental studies which included classic psychedelics, human subjects, and follow-up latencies of at least two weeks. The bulk of this work was published in the last five years, with psilocybin being the most frequently administered drug. Enduring changes in personality/attitudes, depression, spirituality, anxiety, wellbeing, substance misuse, meditative practices, and mindfulness were documented. Mystical experiences, connectedness, emotional breakthrough, and increased neural entropy were related to these long-term changes in psychological functioning. Finally, with proper screening, preparation, supervision, and integration, limited aversive side effects were noted by study participants. Future researchers should focus on including larger and more diverse samples, lengthier longitudinal designs, stronger control conditions, and standardized dosages.

Learning to Let Go: A Cognitive-Behavioral Model of How Psychedelic Therapy Promotes Acceptance

The efficacy of psychedelic-assisted therapies for mental disorders has been attributed to the lasting change from experiential avoidance to acceptance that these treatments appear to facilitate. This article presents a conceptual model that specifies potential psychological mechanisms underlying such change, and that shows substantial parallels between psychedelic therapy and cognitive behavioral therapy: We propose that in the carefully controlled context of psychedelic therapy as applied in contemporary clinical research, psychedelic-induced belief relaxation can increase motivation for acceptance via operant conditioning, thus engendering episodes of relatively avoidance-free exposure to greatly intensified private events. Under these unique learning conditions, relaxed avoidance-related beliefs can be exposed to corrective information and become revised accordingly, which may explain long-term increases in acceptance and corresponding reductions in psychopathology. Open research questions and implications for clinical practice are discussed.

Emotions and brain function are altered up to one month after a single high dose of psilocybin

Psilocybin is a classic psychedelic compound that may have efficacy for the treatment of mood and substance use disorders. Acute psilocybin effects include reduced negative mood, increased positive mood, and reduced amygdala response to negative affective stimuli. However, no study has investigated the long-term, enduring impact of psilocybin on negative affect and associated brain function. Twelve healthy volunteers (7F/5M) completed an open-label pilot study including assessments 1-day before, 1-week after, and 1-month after receiving a 25 mg/70 kg dose of psilocybin to test the hypothesis that psilocybin administration leads to enduring changes in affect and neural correlates of affect. One-week post-psilocybin, negative affect and amygdala response to facial affect stimuli were reduced, whereas positive affect and dorsal lateral prefrontal and medial orbitofrontal cortex responses to emotionally-conflicting stimuli were increased. One-month post-psilocybin, negative affective and amygdala response to facial affect stimuli returned to baseline levels while positive affect remained elevated, and trait anxiety was reduced. Finally, the number of significant resting-state functional connections across the brain increased from baseline to 1-week and 1-month post-psilocybin. These preliminary findings suggest that psilocybin may increase emotional and brain plasticity, and the reported findings support the hypothesis that negative affect may be a therapeutic target for psilocybin.

Therapeutic mechanisms of psilocybin: Changes in amygdala and prefrontal functional connectivity during emotional processing after psilocybin for treatment-resistant depression

BACKGROUND

Psilocybin has shown promise as a treatment for depression but its therapeutic mechanisms are not properly understood. In contrast to the presumed actions of antidepressants, we recently found increased amygdala responsiveness to fearful faces one day after open-label treatment with psilocybin (25 mg) in 19 patients with treatment-resistant depression, which correlated with treatment efficacy.

AIMS

Aiming to further unravel the therapeutic mechanisms of psilocybin, the present study extends this basic activation analysis. We hypothesised changed amygdala functional connectivity, more precisely decreased amygdala-ventromedial prefrontal cortex functional connectivity, during face processing after treatment with psilocybin.

METHODS

Psychophysiological interaction analyses were conducted on functional magnetic resonance imaging data from a classic face/emotion perception task, with the bilateral amygdala and ventromedial prefrontal cortex time-series as physiological regressors. Average parameter estimates (beta weights) of significant clusters were correlated with clinical outcomes at one week.

RESULTS

Results showed decreased ventromedial prefrontal cortex-right amygdala functional connectivity during face processing post- (versus pre-) treatment; this decrease was associated with levels of rumination at one week. This effect was driven by connectivity changes in response to fearful and neutral (but not happy) faces. Independent whole-brain analyses also revealed a post-treatment increase in functional connectivity between the amygdala and ventromedial prefrontal cortex to occipital-parietal cortices during face processing.

CONCLUSION

These results are consistent with the idea that psilocybin therapy revives emotional responsiveness on a neural and psychological level, which may be a key treatment mechanism for psychedelic therapy. Future larger placebo-controlled studies are needed to examine the replicability of the current findings.

Computational chemoproteomics to understand the role of selected psychoactives in treating mental health indications

We have developed the Computational Analysis of Novel Drug Opportunities (CANDO) platform to infer homology of drug behaviour at a proteomic level by constructing and analysing structural compound-proteome interaction signatures of 3,733 compounds with 48,278 proteins in a shotgun manner. We applied the CANDO platform to predict putative therapeutic properties of 428 psychoactive compounds that belong to the phenylethylamine, tryptamine, and cannabinoid chemical classes for treating mental health indications. Our findings indicate that these 428 psychoactives are among the top-ranked predictions for a significant fraction of mental health indications, demonstrating a significant preference for treating such indications over non-mental health indications, relative to randomized controls. Also, we analysed the use of specific tryptamines for the treatment of sleeping disorders, bupropion for substance abuse disorders, and cannabinoids for epilepsy. Our innovative use of the CANDO platform may guide the identification and development of novel therapies for mental health indications and provide an understanding of their causal basis on a detailed mechanistic level. These predictions can be used to provide new leads for preclinical drug development for mental health and other neurological disorders.

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.

REBUS and the Anarchic Brain: Toward a Unified Model of the Brain Action of Psychedelics

This paper formulates the action of psychedelics by integrating the free-energy principle and entropic brain hypothesis. We call this formulation relaxed beliefs under psychedelics (REBUS) and the anarchic brain, founded on the principle that-via their entropic effect on spontaneous cortical activity-psychedelics work to relax the precision of high-level priors or beliefs, thereby liberating bottom-up information flow, particularly via intrinsic sources such as the limbic system. We assemble evidence for this model and show how it can explain a broad range of phenomena associated with the psychedelic experience. With regard to their potential therapeutic use, we propose that psychedelics work to relax the precision weighting of pathologically overweighted priors underpinning various expressions of mental illness. We propose that this process entails an increased sensitization of high-level priors to bottom-up signaling (stemming from intrinsic sources), and that this heightened sensitivity enables the potential revision and deweighting of overweighted priors. We end by discussing further implications of the model, such as that psychedelics can bring about the revision of other heavily weighted high-level priors, not directly related to mental health, such as those underlying partisan and/or overly-confident political, religious, and/or philosophical perspectives. SIGNIFICANCE STATEMENT: Psychedelics are capturing interest, with efforts underway to bring psilocybin therapy to marketing authorisation and legal access within a decade, spearheaded by the findings of a series of phase 2 trials. In this climate, a compelling unified model of how psychedelics alter brain function to alter consciousness would have appeal. Towards this end, we have sought to integrate a leading model of global brain function, hierarchical predictive coding, with an often-cited model of the acute action of psychedelics, the entropic brain hypothesis. The resulting synthesis states that psychedelics work to relax high-level priors, sensitising them to liberated bottom-up information flow, which, with the right intention, care provision and context, can help guide and cultivate the revision of entrenched pathological priors.