Efficacy of psychedelic treatments on depressive symptoms: A meta-analysis

Psychoactive substances for the treatment of neuropsychiatric disorders

In the contemporary landscape of psychiatric medicine, critical advancements have been noted in the utilization of psychoactive substances such as hallucinogens, 3,4-methylenedioxymethamphetamine (MDMA), and ketamine for the treatment of severe mental health disorders. This review provides a detailed evaluation of these substances, focusing on their mechanisms of action and the profound clinical outcomes observed in controlled environments. Hallucinogens like lysergic acid diethylamide and psilocybin primarily target the 5-HT2A receptor agonist-2 (5-HT2AR), inducing substantial perceptual and cognitive shifts that facilitate deep psychological introspection and significant therapeutic advances, particularly in patients suffering from depression and anxiety disorders. MDMA, influencing multiple neurotransmitter systems including 5-Hydroxytryptamine (5-HT), dopamine, and norepinephrine, has been demonstrated to effectively alleviate symptoms of post-traumatic stress disorder, enhancing patients' emotional engagement and resilience during psychotherapy. Meanwhile, ketamine, a glutamate receptor antagonist, rapidly alleviates depressive symptoms, offering a lifeline for individuals with treatment-resistant depression through its fast-acting antidepressant properties. The integration of these substances into psychiatric practice has shown promising results, fundamentally changing the therapeutic landscape for patients unresponsive to traditional treatment modalities. However, the potent effects of these agents also necessitate a cautious approach in clinical application, ensuring careful dosage control, monitoring, and risk management to prevent potential abuse and mitigate adverse effects.

Meditating on psychedelics. A randomized placebo-controlled study of DMT and harmine in a mindfulness retreat

BACKGROUND

In recent years, both meditation and psychedelics have attracted rapidly increasing scientific interest. While the current state of evidence suggests the promising potential of psychedelics, such as psilocybin, to enhance meditative training, it remains equivocal whether these effects are specifically bound to psilocybin or if other classical psychedelics might show synergistic effects with meditation practice. One particularly promising candidate is N,N-dimethyltryptamine (DMT), an active ingredient of ayahuasca.

AIM

This study aims to investigate the effect of the psychedelic substance DMT, combined with the monoamine oxidase inhibitor harmine (DMT-harmine), on meditative states, compared to meditation with a placebo.

METHOD

Forty experienced meditators (18 females and 22 males) participated in a double-blind, placebo-controlled study over a 3-day meditation retreat, receiving either placebo or DMT-harmine. Participants' levels of mindfulness, compassion, insight, and transcendence were assessed before, during, and after the meditation group retreat, using psychometric questionnaires.

RESULTS

Compared to meditation with a placebo, meditators who received DMT and harmine self-attributed greater levels of mystical-type experiences, non-dual awareness, and emotional breakthrough during the acute substance effects and, when corrected for baseline differences, greater psychological insight 1 day later. Mindfulness and compassion were not significantly different in the DMT-harmine group compared to placebo. At 1-month follow-up, the meditators who received DMT and harmine rated their experience as significantly more personally meaningful, spiritually significant, and well-being-enhancing than the meditators who received placebo.

CONCLUSION

Investigating the impact of DMT-harmine on meditators in a naturalistic mindfulness group retreat, this placebo-controlled study highlights the specific effects of psychedelics during meditation.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT05780216.

Psychedelics as a tool for a more connected and sustainable world? Considering the importance of rituals, boundaries, and commitment

Despite the surge of interest in psychedelic research in the past decade, largely due to the promise of psychedelics for improving mental health outcomes, there has been comparatively little discussion about the social and environmental consequences of psychedelic drug use. While there is growing evidence to suggest psychedelics could foster a greater connection to the natural world and improve social relationships, such positive repercussions are far from guaranteed. In this commentary, we focus on LSD, psilocybin and especially MDMA, and outline three insights we came to see as crucial to creating beneficial outcomes: 1) the importance of setting and rituals, 2) the establishment of boundaries, and 3) understanding the long-term commitment required. These insights are grounded in the history of psychedelics, which is intimately intertwined with ritualised use, yet the process of commercialisation of these substances threatens to strip away important contextual factors. Creating boundaries around when, how and with whom psychedelics are used have been found to protect recreational users from harm and could also be instrumental in steering commercial interests to align with socio-environmental goals. Finally, far from being a 'quick fix' for social or environmental problems, the use of psychedelics requires sustained engagement to integrate the insights obtained. Whereas we remain optimistic about the transformative potential of psychedelics for social relationships and the environment, we also emphasise the need for a more cautious, considered approach if we are to harness the benefits and minimise the challenges of psychedelic drug use.

Content analysis of Reddit posts about coadministration of selective serotonin reuptake inhibitors and psilocybin mushrooms

RATIONALE

Treatments with the serotonergic psychedelic psilocybin are being investigated for multiple neuropsychiatric disorders. Because many patients with these disorders use selective serotonin reuptake inhibitors (SSRIs), understanding interactions between psilocybin and SSRIs is critical for evaluating the safety, efficacy, and scalability of psilocybin-based treatments. Current knowledge about these interactions is limited, as most clinical psilocybin research has prohibited concomittant SSRI use.

OBJECTIVES

We aimed to explore potential interactions between psilocybin and SSRIs by characterizing peoples' real-world experiences using psilocybin mushrooms and SSRIs together.

METHODS

We conducted a systematic search of Reddit for posts describing psilocybin mushroom and SSRI coadministration. We identified 443 eligible posts and applied qualitative content analysis to each.

RESULTS

8% of posts reported negative physical or psychological effects resulting from coadministration. These included 13 reports that may reflect serotonin toxicity, and 1 concerning for a psychotic/manic episode. 54% of posts described reduced intensity of the acute psilocybin experience, but 39% reported unchanged intensity with SSRI coadministration.

CONCLUSIONS

Psilocybin's interactions with SSRIs are likely complex and may depend on multiple factors. Prospective studies are needed to evaluate whether psilocybin treatments are reliably safe and effective in the setting of SSRI use.

Safety and risk assessment of psychedelic psychotherapy: A meta-analysis and systematic review

Psychotherapies assisted by psychedelic substances have shown promising results in the treatment of psychiatric disorders. The aim of this systematic review and meta-analysis was to evaluate safety data in human subjects. We carried out a search on MEDLINE, Embase and PsycINFO databases between 2000 and 2022. Standardized mean differences between different dose ranges and between acute and subacute phases were calculated for cardiovascular data after psychedelic administration. Risk differences were calculated for serious adverse events and common side effects. Thirty studies were included in this meta-analysis. There were only nine serious adverse events for over 1000 administrations of psychedelic substances (one during the acute phase and 8 during the post-acute phase). There were no suicide attempts during the acute phase and 3 participants engaged in self-harm during the post-acute phase. There was an increased risk for elevated heart rate, systolic and diastolic blood pressure for all dose range categories, as well as an increased risk of nausea during the acute phase. Other common side effects included headaches, anxiety, and decreased concentration or appetite. This meta-analysis demonstrates that psychedelics are well-tolerated, with a low risk of emerging serious adverse events in a controlled setting with appropriate inclusion criteria.

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=1.64, 95% confidence interval (CI) 0.55 to 2.73, P<0.001) on change in depression scores compared with comparator treatment. Subgroup analyses and metaregressions indicated that having secondary depression (Hedges' g=3.25, 95% CI 0.97 to 5.53), being assessed with self-report depression scales such as the Beck depression inventory (3.25, 0.97 to 5.53), and older age and previous use of psychedelics (metaregression coefficient 0.16, 95% CI 0.08 to 0.24 and 4.2, 1.5 to 6.9, respectively) were correlated with greater improvements in symptoms. All studies had a low risk of bias, but the change from baseline metric was associated with high heterogeneity and a statistically significant risk of small study bias, resulting in a low 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.

The Economics of Treatment for Depression

The global prevalence of depression has risen over the past three decades across all socioeconomic groups and geographic regions, with a particularly rapid increase in prevalence among adolescents (aged 12-17 years) in the United States. Depression imposes large health, economic, and societal costs, including reduced life span and quality of life, medical costs, and reduced educational attainment and workplace productivity. A wide range of treatment modalities for depression are available, but socioeconomic disparities in treatment access are driven by treatment costs, lack of culturally tailored options, stigma, and provider shortages, among other barriers. This review highlights the need for comparative research to better understand treatments' relative efficacy, cost-effectiveness, scalability, and potential heterogeneity in efficacy across socioeconomic groups and country and cultural contexts. To address the growing burden of depression, mental health policy could consider reducing restrictions on the supply of providers, implementing digital interventions, reducing stigma, and promoting healthy lifestyles.

Efficacy and acceptability of psilocybin for primary or secondary depression: A systematic review and meta-analysis of randomized controlled trials

Introduction

Psilocybin is a classic psychedelics, which has been shown to have antidepressant effects by many studies in recent years. In this study, we aim to evaluate the efficacy, acceptability and tolerability of psilocybin in the treatment of primary (major depressive disorder) or secondary (experiencing distress related to life-threatening diagnoses and terminal illness) depression.

Methods

We searched PubMed, EMBASE, Web of Science, Cochrane Library and ClinicalTrials.gov for clinical trials of psilocybin for depression (updated to 4 October, 2023). Effect size Hedges' g was used as an indicator of efficacy, and other outcomes included response rate, drop-out rate, and adverse events.

Results

A total of 10 studies were finally included in systematic review. 8 studies were included in the meta-analysis, involving a total of 524 adult patients, and produced a large effect size in favor of psilocybin (Hedge's g =-0.89, 95% CI -1.25~-0.53, I² = 70.19%, P<0.01). The therapeutic effects of psilocybin increase with increasing doses. Adverse events caused by psilocybin are generally transient and reversible, but serious adverse events also may occur.

Discussion

Our study shows that psilocybin has both short-term and long-term antidepressant effects and holds promise as a potential complementary or alternative therapy for depression, probably. Further research may reveal more about its therapeutic potential.

Giving Consent to the Ineffable

A psychedelic renaissance is currently taking place in mental healthcare. The number of psychedelic-assisted therapy trials is growing steadily, and some countries already grant psychiatrists special permission to use psychedelics in non-research contexts under certain conditions. These clinical advances must be accompanied by ethical inquiry. One pressing ethical question involves whether patients can even give informed consent to psychedelic-assisted therapy: the treatment's transformative nature seems to block its assessment, suggesting that patients are unable to understand what undergoing psychedelic-assisted therapy actually means for them and whether it aligns with their values. The present paper argues that patients often have sufficient knowledge to give informed consent because they know that they want to change their negative status quo and that psychedelic-assisted therapy offers an effective way to do so. Accordingly, patients can understand what the transformative nature of psychedelic-assisted therapy means for them and a make a value-aligned choice even if they are unable to anticipate the manifestation of a psychedelic experience.

The development of psilocybin therapy for treatment-resistant depression: an update

Psilocybin is a classic psychedelic drug that has attracted increasing research interest over the past 10 years as a possible treatment for mood, anxiety and related conditions. Initial phase 2 clinical trials of psilocybin given alongside psychological support for major depression and treatment-resistant depression (TRD) demonstrated encouraging signs of basic safety, further confirmed by a large study in groups of healthy volunteers. The first international multi-centre randomised controlled trial was published in 2022, with signs of efficacy for the 25 mg dose condition in people with TRD when compared with an active placebo. Phase 3 trials in TRD are scheduled to start in 2023. Early evidence suggests that single doses of psilocybin given with psychological support induce rapid improvement in depressive symptoms that endure for some weeks. We therefore provide a timely update to psychiatrists on what psilocybin therapy is, what it is not, and the current state of the evidence-base.

Reduction of alcohol use and increase in psychological flexibility after a naturalistic psychedelic experience: a retrospective survey

INTRODUCTION

Alcohol use can be significantly associated with negative social, professional, and health outcomes. Even more so, alcohol use disorder (AUD) is a critical public health issue and major avoidable risk factor. This study aimed to examine the effect of a naturalistic psychedelic experience on alcohol use and related measures.

METHODS

A retrospective online survey was conducted on 160 individuals who reported a psychedelic experience and a concomitant drinking habit but did not necessarily have an AUD. Demographic data, characteristics of the psychedelic experience, and changes in alcohol consumption and psychological flexibility were surveyed. Results: The mean number of drinking days per week and AUDIT scores significantly decreased after the psychedelic experience (P < .001). Subjects who quit or reduced drinking had a more severe AUD (P < .01) and lower psychological flexibility (P = .003) before the psychedelic session. Alcohol use reduction was significantly associated with the intensity of the mystical experience (P = .03). Psychological flexibility increased more in participants who reduced their alcohol use (P < .001), and the change in psychological flexibility was one of the predictors of alcohol use improvement (P = .003). Conclusion: Our findings suggest that a naturalistic psychedelic experience could be associated with a reduction in alcohol use and dependency. Such positive health outcomes can be associated with the intensity of the mystical experience as well as an increase in psychological flexibility.

Identification of 5-HT2A receptor signaling pathways associated with psychedelic potential

Serotonergic psychedelics possess considerable therapeutic potential. Although 5-HT2A receptor activation mediates psychedelic effects, prototypical psychedelics activate both 5-HT2A-Gq/11 and β-arrestin2 transducers, making their respective roles unclear. To elucidate this, we develop a series of 5-HT2A-selective ligands with varying Gq efficacies, including β-arrestin-biased ligands. We show that 5-HT2A-Gq but not 5-HT2A-β-arrestin2 recruitment efficacy predicts psychedelic potential, assessed using head-twitch response (HTR) magnitude in male mice. We further show that disrupting Gq-PLC signaling attenuates the HTR and a threshold level of Gq activation is required to induce psychedelic-like effects, consistent with the fact that certain 5-HT2A partial agonists (e.g., lisuride) are non-psychedelic. Understanding the role of 5-HT2A Gq-efficacy in psychedelic-like psychopharmacology permits rational development of non-psychedelic 5-HT2A agonists. We also demonstrate that β-arrestin-biased 5-HT2A receptor agonists block psychedelic effects and induce receptor downregulation and tachyphylaxis. Overall, 5-HT2A receptor Gq-signaling can be fine-tuned to generate ligands distinct from classical psychedelics.

Psilocybin-assisted psychotherapy for treatment-resistant depression: Which psychotherapy?

This perspective paper explores the choice of psychotherapy for psilocybin-assisted psychotherapy for treatment-resistant depression. There is evidence to support the use of some psychotherapies in treating 'treatment-resistant' depression, and emerging evidence for the efficacy of psilocybin. The next step which is the focus of this paper is to identify psychotherapies that are both effective and congruent with the psilocybin experience. The evidence for the efficacy of the psychotherapies is drawn from a Cochrane review and the analysis of their congruence with the psilocybin experience is drawn from a qualitative meta-synthesis of the experience of psilocybin. The paper will examine whether three one-to-one psychotherapies identified as effective in the treatment of treatment-resistant depression are compatible with the psilocybin experience. Each psychotherapy will be examined in relation to its congruence with the qualitative evidence that suggests the choice of psychotherapy needs to give priority to the subjective experience, facilitate emotional processing, support connectedness with others, acceptance of the self as emotional and support change based on the person's insights into their relationships with others and the world in which they live. We conclude that interpersonal psychotherapy and intensive short-term dynamic psychotherapy align with that experience, although others are currently being trialled.

Psilocybin-assisted therapy for depression: A systematic review and meta-analysis

The aim of this review was to determine the effect of psilocybin on depressive symptoms in patients diagnosed with life-threatening illnesses or major depressive disorder. Systematic searches were conducted to search for randomized clinical trials and open-label trials that evaluated depression symptoms after psilocybin therapy. Data was pooled using a random-effects model. The primary outcome was the standardized mean difference (SMD) in depression severity, determined by calculating the change in depression ratings from baseline to the primary endpoint in the psilocybin arm versus the control arm. The literature search yielded 1734 studies, and 13 studies (n = 686) were included in either qualitative and/or quantitative analyses. The meta-analysis included 9 studies (pooled n = 596) and yielded a large effect size in favour of psilocybin (SMD = -0.78; p<0.001). Risk ratios for response and remission were large and significant in favour of psilocybin. A review of open-label trials showed robust decreases in depressive symptoms following psilocybin administration. These findings provide preliminary evidence for antidepressant efficacy with psilocybin-assisted psychotherapy, however, further studies are needed to evaluate safety and efficacy and to optimize treatment protocols.

Systematic characterization of Lysergic Acid Diethylamide metabolites in Caenorhabditis elegans by ultra-high performance liquid chromatography coupled with high-resolution tandem mass spectrometry

Psychedelic compounds have gained renewed interest for their potential therapeutic applications, but their metabolism and effects on complex biological systems remain poorly understood. Here, we present a systematic characterization of Lysergic Acid Diethylamide (LSD) metabolites in the model organism Caenorhabditis elegans using state-of-the-art analytical techniques. By employing ultra-high performance liquid chromatography coupled with high-resolution tandem mass spectrometry, we putatively identified a range of LSD metabolites, shedding light on their metabolic pathways and offering insights into their pharmacokinetics. Our study demonstrates the suitability of Caenorhabditis elegans as a valuable model system for investigating the metabolism of psychedelic compounds and provides a foundation for further research on the therapeutic potential of LSD.

Applying Key Lessons from the Hospice and Palliative Care Movement to Inform Psychedelic-Assisted Therapy

Background

Psychedelic-assisted therapy (PAT) has re-emerged as a promising intervention for addressing mental health conditions and existential concerns. Despite growing enthusiasm, PAT may be difficult to integrate into mainstream health systems. The rich sacramental traditions of psychedelics, their centering of the human experience, proposed substrates of action, context-dependent outcomes, and highly relational method of therapy all challenge dominant reductionistic approaches of the biomedical model. Hospice and palliative care are well established as holistic evidence-based standards of care, yet they began as a radical grassroots movement. Hospice and palliative care models may offer unique insights to support the growing field of PAT.

Purpose

The intention of this commentary is to articulate the deep synergies between hospice and palliative care and PAT, with the intention of fostering interdisciplinary dialogue that may aid in implementation of human-centered high-quality PAT.

Conclusions

Various aspects of hospice and palliative care models were identified and explored, which may support the implementation of human-centered high-quality PAT at scale. These include a focus on truly interdisciplinary care, applying a holistic lens to health and illness, bearing witness to suffering and healing, customized care, centering human relationships, decentralized models of care, generalist/specialist competencies, fostering spirituality, organizing as a social moment around shared goals, and growth from grassroots community organizations to mature care systems. Although hospice and palliative care can offer practical lessons for scaling human-centered experiential therapies, PAT, with its radical centering of meaning-making and relationship in the healing process, may also mutually innovate the fields of hospice and palliative care.

Identification of 5-HT2A Receptor Signaling Pathways Responsible for Psychedelic Potential

Serotonergic psychedelics possess considerable therapeutic potential. Although 5-HT2A receptor activation mediates psychedelic effects, prototypical psychedelics activate both 5-HT2A-Gq/11 and β-arrestin2 signaling, making their respective roles unclear. To elucidate this, we developed a series of 5-HT2A-selective ligands with varying Gq efficacies, including β-arrestin-biased ligands. We show that 5-HT2A-Gq but not 5-HT2A-β-arrestin2 efficacy predicts psychedelic potential, assessed using head-twitch response (HTR) magnitude in male mice. We further show that disrupting Gq-PLC signaling attenuates the HTR and a threshold level of Gq activation is required to induce psychedelic-like effects, consistent with the fact that certain 5-HT2A partial agonists (e.g., lisuride) are non-psychedelic. Understanding the role of 5-HT2A-Gq efficacy in psychedelic-like psychopharmacology permits rational development of non-psychedelic 5-HT2A agonists. We also demonstrate that β-arrestin-biased 5-HT2A receptor agonists induce receptor downregulation and tachyphylaxis, and have an anti-psychotic-like behavioral profile. Overall, 5-HT2A receptor signaling can be fine-tuned to generate ligands with properties distinct from classical psychedelics.

Not in the drug, not in the brain: Causality in psychedelic experiences from an enactive perspective

Psychedelics are psychoactive substances that receive renewed interest from science and society. Increasing empirical evidence shows that the effects of psychedelics are associated with alterations in biochemical processes, brain activity, and lived experience. Still, how these different levels relate remains subject to debate. The current literature presents two influential views on the relationship between the psychedelic molecule, neural events, and experience: The integration view and the pluralistic view. The main aim of this article is to contribute a promising complementary view by re-evaluating the psychedelic molecule-brain-experience relationship from an enactive perspective. We approach this aim via the following main research questions: (1) What is the causal relationship between the psychedelic drug and brain activity? (2) What is the causal relationship between brain activity and the psychedelic experience? In exploring the first research question, we apply the concept of autonomy to the psychedelic molecule-brain relationship. In exploring the second research question, we apply the concept of dynamic co-emergence to the psychedelic brain-experience relationship. Addressing these two research questions from an enactive position offers a perspective that emphasizes interdependence and circular causality on multiple levels. This enactive perspective not only supports the pluralistic view but enriches it through a principled account of how multi-layered processes come to interact. This renders the enactive view a promising contribution to questions around causality in the therapeutic effects of psychedelics with important implications for psychedelic therapy and psychedelic research.

Ketamine and serotonergic psychedelics: An update on the mechanisms and biosignatures underlying rapid-acting antidepressant treatment

The discovery of ketamine as a rapid-acting antidepressant spurred significant research to understand its underlying mechanisms of action and to identify other novel compounds that may act similarly. Serotonergic psychedelics (SPs) have shown initial promise in treating depression, though the challenge of conducting randomized controlled trials with SPs and the necessity of long-term clinical observation are important limitations. This review summarizes the similarities and differences between the psychoactive effects associated with both ketamine and SPs and the mechanisms of action of these compounds, with a focus on the monoaminergic, glutamatergic, gamma-aminobutyric acid (GABA)-ergic, opioid, and inflammatory systems. Both molecular and neuroimaging aspects are considered. While their main mechanisms of action differ-SPs increase serotonergic signaling while ketamine is a glutamatergic modulator-evidence suggests that the downstream mechanisms of action of both ketamine and SPs include mechanistic target of rapamycin complex 1 (mTORC1) signaling and downstream GABAA receptor activity. The similarities in downstream mechanisms may explain why ketamine, and potentially SPs, exert rapid-acting antidepressant effects. However, research on SPs is still in its infancy compared to the ongoing research that has been conducted with ketamine. For both therapeutics, issues with regulation and proper controls should be addressed before more widespread implementation. This article is part of the Special Issue on "Ketamine and its Metabolites".

Can psychedelics enhance group psychotherapy? A discussion on the therapeutic factors

BACKGROUND

Despite the growth of psychedelic research, psychedelic-assisted group psychotherapy (PAGP) has received little attention in comparison to individual psychedelic-assisted psychotherapy models.

METHODS

In this article, we aim to discuss the therapeutic potential of PAGP, as well as outline existing models and the challenges of this approach. Using Irvin Yalom's 11 therapeutic factors of group therapy as a basic framework, we analyse current literature from clinical studies and neurobiological research relative to the topic of PAGP.

RESULTS

We argue that combining psychedelic substances and group psychotherapy may prove beneficial for increasing group connectedness and interpersonal learning, potentially enhancing prosocial behaviour with direct opportunities to practice newly acquired knowledge about previously maladaptive behavioural patterns. Challenges regarding this approach include a more rigid therapy structure and potential loss of openness from patients, which may be ameliorated by adequate therapeutic training.

CONCLUSION

We hope for this article to support clinical research on PAGP by presenting a therapeutic framework and outlining its mechanisms and challenges.

The future of psychopharmacology: a critical appraisal of ongoing phase 2/3 trials, and of some current trends aiming to de-risk trial programmes of novel agents

Despite considerable progress in pharmacotherapy over the past seven decades, many mental disorders remain insufficiently treated. This situation is in part due to the limited knowledge of the pathophysiology of these disorders and the lack of biological markers to stratify and individualize patient selection, but also to a still restricted number of mechanisms of action being targeted in monotherapy or combination/augmentation treatment, as well as to a variety of challenges threatening the successful development and testing of new drugs. In this paper, we first provide an overview of the most promising drugs with innovative mechanisms of action that are undergoing phase 2 or 3 testing for schizophrenia, bipolar disorder, major depressive disorder, anxiety and trauma-related disorders, substance use disorders, and dementia. Promising repurposing of established medications for new psychiatric indications, as well as variations in the modulation of dopamine, noradrenaline and serotonin receptor functioning, are also considered. We then critically discuss the clinical trial parameters that need to be considered in depth when developing and testing new pharmacological agents for the treatment of mental disorders. Hurdles and perils threatening success of new drug development and testing include inadequacy and imprecision of inclusion/exclusion criteria and ratings, sub-optimally suited clinical trial participants, multiple factors contributing to a large/increasing placebo effect, and problems with statistical analyses. This information should be considered in order to de-risk trial programmes of novel agents or known agents for novel psychiatric indications, increasing their chances of success.

Psychedelic therapy for depressive symptoms: A systematic review and meta-analysis

BACKGROUND

Psychedelic therapy shows promise for Major Depressive Disorder, especially when treatment-resistant, as well as life-threatening illness distress. The objective of this systematic review, inclusive of meta-analysis, is to examine recent clinical research on the therapeutic effects of classic psychedelics on depressive symptoms.

METHODS

Fourteen psychedelic therapy studies, utilising psilocybin, ayahuasca, or LSD, were systematically reviewed. For the meta-analysis, standardised mean differences were calculated for seven randomised controlled trials.

RESULTS

The systematic review indicated significant short- and long-term reduction of depressive symptoms in all conditions studied after administration of psilocybin, ayahuasca, or LSD, with psychological support. In the meta-analysis, symptom reduction was significantly indicated in three timepoints out of four, including 1-day, 1-week, and 3-5 weeks, supporting the results of the systematic review, with the exception of the 6-8 weeks follow-up point which was less conclusive.

LIMITATIONS

The absence of required data for 2 studies necessitated the less precise use of graphical extraction and imputation. The small sample size in all but one study negatively affected the statistical power. None of the studies had long-term follow-up without also utilising the cross-over method, which did not allow for long-term results to be included in the meta-review.

CONCLUSIONS

This review indicates an association between psychedelic therapy and significant reduction of depressive symptoms at several time points. However, the small number of studies, and low sample sizes, calls for careful interpretation of results. This suggests the need for more randomised clinical trials of psychedelic therapy, with larger and more diverse samples.

Linkages between Psychedelics and Meditation in a Population-Based Sample in the United States

There are neurophysiological and phenomenological overlaps between psychedelic and meditative states, but there is little evidence on how exposure to psychedelics might be associated with meditation-related variables. We assessed lifetime classic psychedelic use, ego dissolution during one's most intense experience using a classic psychedelic, and exposure to meditation in a representative sample (n = 953) of American adults. Those who reported experience with meditation were invited to complete a follow-up survey (n = 536, 92.1% response rate) measuring meditation-related variables. Models controlled for a range of potential confounds. Exposure to meditation was associated with lifetime classic psychedelic use and ego dissolution in covariate-adjusted models. In addition, among meditators, greater ego dissolution was associated with more frequent meditation practice. Both lifetime classic psychedelic use and ego dissolution were associated with enlightenment as motivation to practice meditation as well as lower likelihood of overall perceived barriers to meditation practice. Ego dissolution was positively associated with finding meditation more effective. Neither lifetime classic psychedelic use nor ego dissolution was associated with greater likelihood of meditation-related adverse effects. Taken together, results support potential synergy between psychedelics and meditation, but randomized controlled trials are necessary to establish safety and evaluate potential causal relationships.

How Important Is a Guide Who Has Taken Psilocybin in Psilocybin-Assisted Therapy for Depression?

Promising outcomes of Psilocybin-Assisted Therapy (PAT) for depression have generated concerted efforts to replicate, extend, and refine protocols to maximize efficacy. Psychotherapy research reveals that clients benefit most when important components of treatment align with their personal preferences. One open question related to PAT concerns the importance of the psilocybin experience of the guides (trained professionals present during acute effects). We sought to assess the importance of a guide who had used psilocybin to potential clients with depressive symptoms. Over 800 MTurk respondents with depressive symptoms rated the import of a guide who had used psilocybin relative to alternative characteristics in guides and cognitive behavioral (CBT) therapists. Importance ratings for guides who had used psilocybin significantly exceeded the "somewhat important" level (50 on a 0-100 scale), other guide-related qualities, and comparable ratings for a cognitive behavioral therapist who shared demographics, had experience with depression and received cognitive therapy personally. People of color (those who are not Caucasian) and those who had previous therapy gave significantly higher importance ratings for guides who had used psilocybin. Participants who chose to list other qualities important for guides listed very similar ones for CBT therapists, often emphasizing proper training and an empathic demeanor. Guides who have used psilocybin, who inform clients of the fact, might have advantages for facilitating PAT's antidepressant effects, as least in a subset of clients.

Exploring the Credibility of Psilocybin-assisted Therapy and Cognitive-behavioral Therapy for Depression

Depression treatments succeed with many but leave others unimproved, and they can generate concerns about side effects, time, and cost. Psilocybin has generated media attention and empirical support for antidepressant effects, but lay impressions of its effectiveness are unclear. Although perceptions of treatment credibility contribute to outcome, beliefs about the credibility of psilocybin-assisted therapy (PAT) among potential patients remain uninvestigated, especially relative to cognitive-behavioral therapy (CBT), a common, empirically-validated approach. The present study examined credibility ratings for CBT and PAT among individuals reporting depressive symptoms. Participants (N = 803) from Amazon's MTurk platform reported demographics, depressive symptoms, and psychotherapy experience, then read data-based vignettes describing each therapy and rated their credibility. Individuals rated CBT as more credible than PAT. Those with therapy experience rated CBT as more credible than those without. Men and lifetime hallucinogen users rated PAT more credible than women and non-users, but few other predictors accounted for much variance in credibility. Results suggest that potential clients appear cautious about PAT. As continued work examines the effectiveness of psychedelic-assisted interventions, researchers and clinicians must consider patients' beliefs about treatments as potential predictors of outcomes. Additionally, the paradigm used here might have potential for examining credibility of many interventions.

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.

Reasonable expectations for replications of psychedelic-assisted therapy: The case for prediction intervals rather than P-values

Psychedelic compounds hold promise for alleviating human suffering. Initial trials of psychedelic-assisted treatments have established feasibility and safety, generating calls for replications. Meanwhile, social and medical sciences have drawn criticism due to perceptions of replication failures and varying public trust in empiricism. Data suggest that researchers and the public frequently misunderstand some of the statistical issues associated with replication, potentially leading to unrealistic expectations of treatment effects. Promoting discourse on what constitutes sufficient replication is especially warranted considering the ongoing progression of multi-site phase II and III clinical trials. Here, we review recent and classic work on prediction intervals and power analysis to reveal that trials of psychedelic-assisted therapy that emphasize statistical significance will likely include failures to replicate, especially if sample sizes do not increase dramatically. The field and the public should expect some failed replication attempts based on sampling variability alone. Continued emphasis on statistical significance will require markedly larger samples than those used in clinical trials to date, necessitating substantially greater resources. An alternative approach focused on prediction intervals has distinct advantages. We focus on a recent trial of MDMA-assisted therapy for PTSD to show that, based on prediction intervals, reasonable replications are well within reach. A lack of attention to these statistical issues could unnecessarily prompt widespread dismissal of these therapies before the intervention receives adequate investigation and a fair assessment. In contrast, realistic expectations and appropriate planning could help ensure that these treatments receive the opportunity to help those most in need.

Ayahuasca and tobacco smoking cessation: results from an online survey in Brazil

RATIONALE

Smoking-related disease is a major problem globally. Effective smoking cessation treatments are however limited. Increasing evidence suggests that psychedelics have potential as treatments for substance use disorders and may therefore prove an option in aiding smoking cessation.

OBJECTIVES

To establish which factors predict smoking cessation in people who reported quitting or reducing smoking following ayahuasca consumption.

METHODS

A retrospective cross-sectional mixed-method study (quantitative and qualitative design) was undertaken using data from an online survey evaluating peoples' experiences before and after drinking ayahuasca. Multivariate logistic regression was performed with smoking condition (cessation or reduction/relapse) as a dependent variable and demographics, smoking, ayahuasca-related variables and the mystical experience (MEQ30) as predicting factors.

RESULTS

A total of 441 responses were grouped according to self-reported smoking status: cessation (n = 305) or reduction/relapse (n = 136) smoking. Logistic regression showed that mystical experience (OR: 1.03; 95% CI [1.00-1.05]) and frequency of ayahuasca intake (OR: 2.16[1.00-4.70]) were protective factors, while positive mood (measured by the MEQ30) during the ayahuasca experience was a risk factor (OR: 0.91[0.85-0.97]). Qualitative thematic analysis identified eight themes (e.g. acquired awareness, spiritual experience, increased motivation) related to the ayahuasca experience and the process of smoking cessation/reduction.

CONCLUSIONS

Our results suggest that ayahuasca could be used as a potential tool for smoking cessation, and that effects may be mediated by mystical experience. Given the current burden of smoking-related disease and the limited treatment options, studies are needed to investigate the efficacy of psychedelics in smoking cessation.

Trajectory of Antidepressant Effects after Single- or Two-Dose Administration of Psilocybin: A Systematic Review and Multivariate Meta-Analysis

We examined the cardiovascular safety, acceptability, and trajectory of the antidepressant effects of psilocybin after single- or two-dose administration. Four major electronic databases were systematically searched. Data were pooled using a multivariate random-effects meta-analysis. Primary outcomes were changes in depressive symptoms. Secondary outcomes were cardiovascular safety and acceptability. Ten studies were included. The estimated effect sizes (standardized mean difference (SMD) with 95% confidence intervals) for psilocybin were −0.75 (−1.15 to −0.35) on day 1, −1.74 (−2.15 to −1.32) at 1 week, −1.35 (−1.77 to −0.93) at 1 month, −0.91 (−1.31 to −0.51) at 3 months, and −1.12 (−1.56 to −0.68) at 6 months. Higher doses and two sessions of psilocybin treatment were significantly associated with superior antidepressant effects. The all-cause discontinuation and heart rate after psilocybin administration were comparable to placebo; meanwhile, psilocybin increased systolic and diastolic blood pressure by 19.00 mmHg and 8.66 mmHg, respectively. There were no significant differences between SMD derived from placebo-controlled trials compared to those from pre–post changes and SMD in randomized controlled trials (RCTs) compared to those in non-RCTs. The present study demonstrates that single- or two-dose psilocybin administration has rapid and sustained antidepressant effects for up to 6 months, with favorable cardiovascular safety and acceptability.

A retrospective analysis of the "Neverending Trip" after administration of a potent full agonist of 5-HT2A receptor - 25I-NBOMe

BACKGROUND

5-HT2A receptor (e.g. 25I-NBOMe) agonists not only pose risks of acute intoxication but also long-term effects and significant adverse reactions, e.g. hallucinogen persisting perception disorder (HPPD), derealization, and depersonalization.

AIMS

We evaluated the risk associated with single and repeated use of 25I-NBOMe. We aimed to identify factors that may increase the risk of HPPD, increase its severity and determine the time when the first symptoms appear. Herein, we report the first extensive evaluation of 25I-NBOMe-induced HPPD.

METHOD

We assessed all reports (58) collected by The Pomeranian Pharmacovigilance Centre (PPC) from 2013 to 2020.

RESULTS

The study included a total of 58 reports of adverse reactions caused by 25I-NBOMe. In the case of 15 reports (in patients aged 19-26 years), symptoms persisted many months after the discontinuation of 25I-NBOMe. The most common were: pseudohallucinations, bizarre delusions, derealizations and in some cases development or worsening of depression has been diagnosed. HPPD-like symptoms were most common in patients who took the drug regularly (i.e., several times a month). The risk of HPPD-like symptoms is higher in patients who have severe visual pseudohallucinations, severe bizarre delusions, derealization and/or depersonalization onset immediately after taking the drug. Recurrence of HPPD symptoms may be provoked by many factors, however, there is some cases there is no apparent reason. HPPD after 25I-NBOMe use can last from 2 months up to 2 years. In some patients, pharmacological treatment was necessary due to 25I-NBOMe-induced HPPD and depression.

CONCLUSIONS

The study showed long-lasting effects after 25I-NBOMe administration and allowed for the determination of HPPD risk factors.

Psychedelic use is associated with reduced daily opioid use among people who use illicit drugs in a Canadian setting

BACKGROUND

Research into the therapeutic and naturalistic uses of psychedelics for improving outcomes related to mental health disorders has generated increasing interest in recent years. While controlled clinical trials of psychedelics have signaled benefits for treating substance use disorders, this area has not been well studied in the context of naturalistic psychedelic use. This study sought to investigate the possible relationship between recent naturalistic psychedelic use and subsequent daily illicit opioid use among people who use drugs (PWUD).

METHODS

Data (2006-2018) were drawn from three harmonized prospective cohorts of community-recruited PWUD in Vancouver, Canada. We used multivariable generalized linear mixed-effects modeling (GLMM) to estimate the independent association between psychedelic use and subsequent daily illicit opioid use.

RESULTS

Among 3813 PWUD at baseline, 1093 (29%) reported daily use of illicit opioids and 229 (6%) reported psychedelic use in the past six months. Over study follow-up after adjusting for a range of potential confounders, psychedelic use remained independently associated with a significantly reduced odds of subsequent daily opioid use (Adjusted Odds Ratio: 0.45; 95% Confidence Interval: 0.29 to 0.70).

CONCLUSION

While confirmation in other settings is required, these findings align with growing evidence that psychedelic use may be associated with detectable reductions in subsequent substance use including illicit opioid use.

Psychedelics, Mystical Experience, and Therapeutic Efficacy: A Systematic Review

The mystical experience is a potential psychological mechanism to influence outcome in psychedelic therapy. It includes features such as oceanic boundlessness, ego dissolution, and universal interconnectedness, which have been closely linked to both symptom reduction and improved quality of life. In this review, 12 studies of psychedelic therapy utilizing psilocybin, ayahuasca, or ketamine were analyzed for association between mystical experience and symptom reduction, in areas as diverse as cancer-related distress, substance use disorder, and depressive disorders to include treatment-resistant. Ten of the twelve established a significant association of correlation, mediation, and/or prediction. A majority of the studies are limited, however, by their small sample size and lack of diversity (gender, ethnic, racial, educational, and socioeconomic), common in this newly re-emerging field. Further, 6 out of 12 studies were open-label in design and therefore susceptible to bias. Future studies of this nature should consider a larger sample size with greater diversity and thus representation by use of randomized design. More in-depth exploration into the nature of mystical experience is needed, including predictors of intensity, in order to maximize its positive effects on treatment outcome benefits and minimize concomitant anxiety. Systematic Review Registration: PROSPERO, identifier CRD42021261752.

Assessing the effects of methodological differences on outcomes in the use of psychedelics in the treatment of anxiety and depressive disorders: A systematic review and meta-analysis

BACKGROUND

Classical psychedelics are a group of drugs which act as agonists on the serotonin-2A (5-HT2A) receptor. Evidence suggests they may have a uniquely rapid and enduring positive effect on mood. However, marked heterogeneity between methodological designs in this emerging field remains a significant concern.

AIMS

To determine how differences in the type of psychedelic agent used and the number of dosing sessions administered affect subjects' depression and anxiety outcomes and adverse drug reactions (ADR).

METHODS

This review collected and screened 1591 records from the MEDLINE and Web of Science databases for clinical trials reporting objective data on mood for subjects with a known anxiety or depression.

RESULTS

After screening, nine clinical trials met inclusion criteria. Meta-analysis of these studies showed significant, large positive effect sizes for measures of anxiety (Cohen's d = 1.26) and depression (Cohen's d = 1.38) overall. These positive effects were also significant at acute (⩽1 week) and extended (>1 week) time points. No significant differences were observed between trials using different psychedelic agents (psilocybin, ayahuasca or lysergic acid diethylamide (LSD)), however, a significant difference was observed in favour of trials with multiple dosing sessions. No serious ADR were reported.

CONCLUSION

Psilocybin, ayahuasca and LSD all appear to be effective and relatively safe agents capable of producing rapid and sustained improvements in anxiety and depression. Moreover, the findings of the present analysis suggest that they may show a greater efficacy when given to patients over multiple sessions as compared to the more common single session used in many of the existing trials.

Overcoming Depression with 5-HT2A Receptor Ligands

Depression is a multifactorial disorder that affects millions of people worldwide, and none of the currently available therapeutics can completely cure it. Thus, there is a need for developing novel, potent, and safer agents. Recent medicinal chemistry findings on the structure and function of the serotonin 2A (5-HT2A) receptor facilitated design and discovery of novel compounds with antidepressant action. Eligible papers highlighting the importance of 5-HT2A receptors in the pathomechanism of the disorder were identified in the content-screening performed on the popular databases (PubMed, Google Scholar). Articles were critically assessed based on their titles and abstracts. The most accurate papers were chosen to be read and presented in the manuscript. The review summarizes current knowledge on the applicability of 5-HT2A receptor signaling modulators in the treatment of depression. It provides an insight into the structural and physiological features of this receptor. Moreover, it presents an overview of recently conducted virtual screening campaigns aiming to identify novel, potent 5-HT2A receptor ligands and additional data on currently synthesized ligands acting through this protein.

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.

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.

New Insights Into the Clinical and Nonclinical Effects of Psychedelic Substances

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

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.

Cannabis-induced oceanic boundlessness

BACKGROUND

Despite tetrahydrocannabinol (THC)'s reputation for creating dramatic effects at high doses, empirical work rarely addresses cannabis's impact on subjective responses common to the tryptamine psychedelics. We focused on these effects because they have preceded and covaried with the therapeutic impact of psilocybin in previous work.

AIMS

The current study examined if self-reported responses to cannabis products might parallel those found in clinical trials of psilocybin administration. We also investigated if measures of demographics and cannabis use might correlate with these responses.

METHODS

Participants reported the subjective effect of their highest THC experience using 27 items that assess oceanic boundlessness, a correlate of mystical experiences. They also answered infrequency items and questions on demographics and cannabis consumption.

RESULTS

In an effort to address concerns about replication, we divided respondents who passed infrequency items into two random samples. Self-reported "breakthrough" experiences were significantly greater than zero but significantly lower than those reported in randomized clinical trials of psilocybin (17-19% vs. 59%). Total scores covaried with perceived dosages of THC, but only in one sample. Heavier users of cannabis reported lower scores.

CONCLUSIONS

Self-report data suggest that high doses of cannabis can create subjective effects comparable to those identified in trials of psilocybin that precede relief from cancer-related distress, treatment-resistant depression, alcohol problems, and cigarette dependence. Given the disparate mechanisms of action, comparing THC-induced to psilocybin-induced effects might improve our understanding of the mechanisms underlying subjective experiences. This work might also support the development of a cannabis-assisted psychotherapy comparable to psilocybin-assisted psychotherapy.

Symptom specificity of ayahuasca's effect on depressive symptoms

Background

Ayahuasca's effects on symptoms of depression have generated considerable optimism. Clients frequently report more concern about some symptoms than others, and available treatments alter symptoms differentially. Few studies address the symptom specificity of this psychoactive brew.

Aims

We examined self-reported effects of ayahuasca on the individual symptoms of depression assessed by the 10-item short-form of Center for Epidemiological Studies of Depression (CESD-10).

Methods

We asked over 120 participants to complete a retrospective assessment of CESD-10 symptoms one month before and one month after using ayahuasca.

Results

Participants indicated that ayahuasca had a larger influence on affective symptoms like hope, depressed mood, and happiness, than cognitive, interpersonal, and somatic symptoms like restless sleep, loneliness, and difficulty focusing.

Conclusions

Potential clients might appreciate identifying if different treatments provide more relief for some depressive symptoms than others. We examined retrospective reports of ayahuasca's potential for differential impact. Those eager to alter hope, happiness, and other affective symptoms will likely find ayahuasca more helpful than those who want an intervention for restless sleep, loneliness, or trouble focusing. This symptom specificity parallels the effects of serotonergic antidepressant medications, suggesting that psychedelic-assisted psychotherapy using ayahuasca might have considerable appeal for those who seek comparable relief but would rather not use prescription serotonergic medications. Jumpstarting psychotherapy with the rapid onset of ayahuasca-induced relief also appears to have potential.

[Efficacy of psychedelics in psychiatry, a systematic review of the literature]

OBJECTIVES

Psychedelics are powerful psychoactive substances. Natural psychedelics have been used for millennia by human civilizations, in particular in Latin America, while synthetic psychedelics were discovered in the 50s, giving rise to a lot of research before they were prohibited. More recently, their therapeutic properties have been studied especially to help patients with psychiatric conditions, psychological distress or substance use disorders. This article is a systematic review of the literature which aims to provide an overview of all studies that assessed the efficacy of psychedelics, i.e. psilocybin, ayahuasca and lysergic acid diethylamide (LSD), on psychiatric diseases and addictions.

METHODS

We conducted this literature review following the PRISMA recommendations. MEDLINE, PsycInfo, Web of Science and Scopus were searched from January 1990 to May 2020 with the following keywords "(ayahuasca OR psilocybin OR lysergic acid diethylamide) AND (depression OR anxiety OR major depressive disorder OR bipolar disorder OR anxiety disorder OR substance use disorder OR dependence)".

RESULTS

Twenty-five articles met the inclusion criteria. Five articles studied psychedelic efficacy in the treatment of life-threatening diseases related to anxiety and depression: four were randomized controlled crossover trials (three with psilocybin for a total of 92 patients, and one with LSD, n=12), and one was a long-term follow-up study. Eleven articles explored the efficacy of psychedelics in the treatment of major depressive episodes: two were open-labeled trials (one with ayahuasca, n=17, one with psilocybin, n=20), one was a randomized controlled trial using ayahuasca against placebo (n=29), and the others were long-term follow-up studies or assessed more precise dimensions of the depressive disorder, such as suicidality, emotion processing or personality traits. Eight articles studied the efficacy of psychedelics in the treatment of addictions: two were open-labeled studies using psilocybin (one in alcohol use disorder, n=10, and one in tobacco use disorder, n=15), and the others were long-term follow-up studies or retrospective observational descriptive studies on alcohol, tobacco, opioids, cannabis, and psychostimulants. One study explored the efficacy of psilocybin in obsessional-compulsive disorder (n=9). Overall, these studies found a quick and important response after psychedelic administration that lasted for several months, even after a single dose. However most of these studies were descriptive or open-label studies conducted on small size samples. No severe adverse events occurred.

CONCLUSIONS

Psychedelics are promising treatments for anxiety, depression and addiction, their efficacy is quick and sustainable, and they are well tolerated. These effects need to be confirmed in larger studies and compared to standard care.

Comparative effects of (S)-ketamine and racemic (R/S)-ketamine on psychopathology, state of consciousness and neurocognitive performance in healthy volunteers

Ketamine and its (S)-enantiomer show distinct psychological effects that are investigated in psychiatric research. Its antidepressant activity may depend on the extent and quality of these psychological effects which may greatly differ between the enantiomers. Previous data indicate that the (S)-ketamine isomer is a more potent anesthetic than (R)-ketamine. In contrast, in subanesthetic doses (R)-ketamine seems to elicit fewer dissociative and psychotomimetic effects compared to (S)-ketamine. In this randomized double-blind placebo-controlled trial the effects of (R/S)-ketamine and (S)-ketamine on standardized neuropsychological and psychopathological measures were compared. After an initial bolus equipotent subanesthetic doses of (R/S)- and (S)-ketamine or placebo were given by continuous intravenous infusion to three groups of 10 healthy male volunteers each (n = 30). (R/S)-Ketamine and (S)-ketamine produced significant psychopathology and neurocognitive impairment compared to placebo. No significant differences were found between (R/S)-ketamine and (S)-ketamine. (S)-Ketamine administration did not result in reduced psychopathological symptomatology compared to (R/S)-ketamine as suggested by previous studies. However, this study revealed a somewhat more "negatively experienced" psychopathology with (S)-ketamine, which opens questions about potential "protective effects" associated with the (R)-enantiomer against some psychotomimetic effects induced by the (S)-enantiomer. As the antidepressant effect of ketamine might depend on a pleasant experience of altered consciousness and perceptions and avoidance of anxiety, the ideal ketamine composition to treat depression should include (R)-ketamine. Moreover, since preclinical data indicate that (R)-ketamine is a more potent and longer acting antidepressant compared to (S)-ketamine and (R/S)-ketamine, randomized controlled trials on (R)-ketamine and comparative studies with (S)-ketamine and (R/S)-ketamine are eagerly awaited.

Recent developments in geriatric psychopharmacology

INTRODUCTION

There is a tremendous growing need to address the burden of geriatric psychiatric disorders. Recent developments relevant to geriatric psychiatry have focused on Alzheimer's disease (AD), severe/refractory depression, and cancer/end of life care.

AREAS COVERED

This is a non-systematic, narrative review (databases and websites for search: PubMed, Google Scholar, Medscape, ClinicalTrials.gov; focusing on the last 6 years), and covers developments in disease-modifying therapies for AD, diagnostic radiotracers for AD, medications for neuropsychiatric symptoms of dementia, ketamine/esketamine, psychedelics, and cannabinoids.

EXPERT OPINION

The focus of on-going trials of anti-amyloid agents has been on individuals with very early stage AD; several agents are under phase 3 investigation, and aducanumab is under FDA review. Amyloid and tau PET scans have been approved by the FDA to assist in the diagnoses of AD. Promising pharmaceuticals for neuropsychiatric symptoms of dementia include pimavanserin, brexpiprazole, escitalopram, dextromethorphan/quinidine, and lithium. Esketamine, although approved for treatment-resistant depression in general adults, failed to demonstrate efficacy in elderly patients in a phase 3 trial. There is preliminary evidence for benefit of psychedelic-assisted psychotherapy in end-of-life and cancer-related depression/anxiety. Evidence for the use of cannabinoids is currently lacking.

Classic serotonergic psychedelics for mood and depressive symptoms: a meta-analysis of mood disorder patients and healthy participants

RATIONALE

Major depressive disorder is one of the leading global causes of disability, for which the classic serotonergic psychedelics have recently reemerged as a potential therapeutic treatment option.

OBJECTIVE

We present the first meta-analytic review evaluating the clinical effects of classic serotonergic psychedelics vs placebo for mood state and symptoms of depression in both healthy and clinical populations (separately).

RESULTS

Our search revealed 12 eligible studies (n = 257; 124 healthy participants, and 133 patients with mood disorders), with data from randomized controlled trials involving psilocybin (n = 8), lysergic acid diethylamide ([LSD]; n = 3), and ayahuasca (n = 1). The meta-analyses of acute mood outcomes (3 h to 1 day after treatment) for healthy volunteers and patients revealed improvements with moderate significant effect sizes in favor of psychedelics, as well as for the longer-term (16 to 60 days after treatments) mood state of patients. For patients with mood disorder, significant effect sizes were detected on the acute, medium (2-7 days after treatment), and longer-term outcomes favoring psychedelics on the reduction of depressive symptoms.

CONCLUSION

Despite the concerns over unblinding and expectancy, the strength of the effect sizes, fast onset, and enduring therapeutic effects of these psychotherapeutic agents encourage further double-blind, placebo-controlled clinical trials assessing them for management of negative mood and depressive symptoms.

Cross-Sectional Associations Between Lifetime Use of Psychedelic Drugs and Psychometric Measures During the COVID-19 Confinement: A Transcultural Study

Background: One of the main public health strategies adopted at the beginning of the COVID-19 pandemic consisted of implementing strict lockdowns to stop the transmission of the virus. Despite being an effective measure, the confinement and the associated social isolation create a stressful, potentially lengthy situations that has been proven to have several psychological consequences. Given the potential benefits that certain psychedelic drugs have shown for the treatment of psychological disorders, this study aimed to assess the impact of lifetime psychedelic drug use on mental health in relation to the first strict lockdown adopted by various countries (April-July 2020). Methods: Subjects completed an online survey that inquired about sociodemographic factors, activities, and lifestyle factors during confinement, as well as health and mental health related factors. Subjects were asked about their lifetime use of psychedelic drugs (MDMA, ayahuasca, psilocybin-containing mushrooms, LSD, peyote, San Pedro, Bufo alvarius or 5-MeO-DMT, and others), being classified as regular users (more than once per 6 months), occasional users, or non-users. The survey included psychometric tests used to assess psychological distress, peritraumatic stress, social support, psychopathological symptoms, and personality. Linear regressions were performed with psychedelic drug users as the independent variable and psychometric factors as the outcomes, while correcting for age, gender, language, religion, spirituality, and use of non-psychedelic drugs. Results: The study included 2,974 English, Portuguese, and Spanish speakers (497 regular users of psychedelic drugs, 606 occasional users, and 1,968 non-users). On average, respondents were 36 years old and 70% were female. Psychedelic drug users, especially regular ones, reported less psychological distress, less peritraumatic stress, and more social support. Regarding personality measures, psychedelic drug users scored higher on the novelty-seeking and self-transcendence scales, and lower on cooperativeness. Conclusion: Our findings showed that regular users of psychedelic drugs had less psychological stress and some personality differences when compared to occasional users and non-users. This suggests that either the use of psychedelics might be a protective factor itself or people with certain previous traits are more prone to frequently using psychedelic drugs. Future prospective longitudinal research should investigate the underlying processes observed in this study to develop consistent hypotheses.

Psychedelic Mushrooms in the USA: Knowledge, Patterns of Use, and Association With Health Outcomes

Introduction: Popular media coverage of psychedelics use, growing research into this class of compounds for psychiatry and decriminalization initiatives, are transforming the public perception of psychedelics. However, little is known about levels of knowledge and psychedelic mushroom (PM) use among American adults. Methods: We examined PM use and various measures of health status, quality of life, and self-reported mental health outcome measures obtained through a national on-line, cross-sectional survey of adults with a demographic composition representative of the US adult population by region, gender, age, and race (weighted N = 251,297,495) from November 2020-March 2021. Results: General mental health and well-being were popular reasons for PM use (63.6%), although use for medically-diagnosed (31.8%) and self-diagnosed (19.0%) conditions was also common. PM users reported more depression and anxiety as reflected in higher GAD-7 and PHQ-9 scores. Factors predictive of PM use included being male [OR 1.54 95%CI 1.09-2.15] and having higher Charlson Comorbidity Index scores [OR 1.42; 95%CI 1.22-1.65]. Self-reported PM use was less likely among participants with health insurance [OR = 0.50 (0.35-0.72)], increased age [OR = 0.92 (0.90-0.93)] and, relative to those living in the west US census region, living in the northeast [OR = 0.27 (0.15-0.50)], midwest [OR = 0.34 (0.20-0.56)], and south [OR = 0.38 (0.26-0.55)]. Discussion and Conclusions: A significant number of Americans are already "self-medicating" with PM and as growing positive media coverage of psychedelics drives public interest in the health benefits of PM, this number will increase. The association between PM use and poor mental health requires further research to inform policy.