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Brandon Weiss

American University, Washington College

27 papers in the library · 736 citations · publishing 2020-2026

Papers

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Effects of an international ceremonial ayahuasca retreat on the diversity and community composition of the human gut microbiome: A preliminary observational single-arm pre-post study

Brain Behavior and Immunity Integrative July 1, 2026 Lyanna R. Kessler, Lamya'a Dawud, John D. Sterrett et al.

ABSTRACT Posttraumatic stress disorder (PTSD) is a mental health condition that can develop following exposure to a traumatic event, often with persistent anxiety and depressive symptoms. Recent research suggests the microbiome-gut-brain axis may play an important role in the etiology and pathophysiology of PTSD. At the same time, retreats incorporating psychedelic-assisted therapies have...

Detecting neuroplastic effects induced by ketamine in healthy human subjects: A multimodal approach.

Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism March 21, 2026 Claudio Agnorelli, Joseph Peill, Gabriela Sawicka et al.

We investigated ketamine's neuroplastic effects in healthy human subjects using integrated Positron Emission Tomography (PET)/Magnetic Resonance Imaging (MRI) measures before and 1-8 days after a single psychedelic dose of ketamine (1 mg/kg, intravenous). Eleven male participants underwent two PET/MRI scans with [11C]-UCBJ (synaptic density/plasticity), 1H-MRS (glutamate and GABA) and...

A short-acting psychedelic intervention for major depressive disorder: a phase IIa randomized placebo-controlled trial.

Nat Med February 16, 2026 David Erritzøe, Tommaso Barba, Tiffanie Benway et al. 4 citations

Major depressive disorder (MDD) is a leading cause of disability worldwide, yet many patients have inadequate responses to current treatments. Dimethyltryptamine (DMT), a serotonergic psychedelic with rapid onset and short duration, shows promise as a potential antidepressant (AD), although clinical evidence in MDD remains limited. We conducted a phase IIa, double-blind, placebo-controlled,...

Neutral attitude toward the utilization of psychedelic therapy for depression in the United Kingdom population.

The International journal on drug policy November 1, 2025 Liam O Jarvis, Alexander H Jack, Niall Galbraith et al. 1 citation

The global prevalence of depression is high, and there are concerns about the therapeutic effectiveness of current treatments. Research over the past two decades has led to a new class of alternative treatments termed 'psychedelic-assisted therapy (PAT).' This study aimed to investigate the attitudes toward the application and use of psychedelic-assisted therapies in the United Kingdom...

A Field-Wide Review and Analysis of Study Materials Used in Psilocybin Trials: Assessment of Two Decades of Research

Psychedelic Medicine January 20, 2025 Marianna Graziosi, Gabrielle Agin-Liebes, Mary P Cosimano et al. 9 citations

Introduction: Serotonergic psychedelics, serotonin 2A receptor agonists such as psilocybin that can result in substantially altered states of consciousness, are used in recreational and research settings. The safety of psychedelic experiences in research settings is supported by controlled physical environments, presence of clinical and medical staff to address emergent issues, screening for...

An investigation of acute physiological and psychological moderators of psychedelic-induced personality change among healthy volunteers

Neuroscience Applied December 2, 2024 Kate Godfrey, Brandon Weiss, Joseph Peill et al. 5 citations

This study investigated the effects of a single high-dose of psilocybin on personality traits in psychedelic-naïve healthy volunteers. These data originate from a larger within-subjects fixed-order design trial, where a single high dose of psilocybin (25 mg) was administered in a psychologically supportive setting and was compared against a (one-month) prior, 1 mg 'placebo' dose. Personality...

Ayahuasca in the treatment of posttraumatic stress disorder: Mixed-methods case series evaluation in military combat veterans.

Psychological trauma : theory, research, practice and policy December 1, 2024 Brandon Weiss, Lê-Anh Dinh-Williams, Nick Beller et al. 16 citations

[Correction Notice: An Erratum for this article was reported online in Psychological Trauma: Theory, Research, Practice, and Policy on Jul 25 2024 (see record 2025-07042-001). In the original article, there was an error in the calculations that led to the overstatement of the symptom severity of the veteran sample. Specifically, sum scores for the posttraumatic stress disorder (PTSD) symptom...

Preliminary Evidence of Sleep Improvements Following Psilocybin Administration, and their Involvement in Antidepressant Therapeutic Action

Current Psychiatry Reports November 1, 2024 Matthew J Reid, Hannes Kettner, Tessa F. Blanken et al. 4 citations

Abstract Purpose of the study Psilocybin is a rapidly-emerging treatment for depression, yet its impact on sleep is not well understood. We sought to explore the literature on sleep and psilocybin use, and explore the topic using our own primary data. Findings Whilst clinical trials demonstrate large depressive symptom improvements, the impact of psilocybin on sleep quality or insomnia...

Effect of psilocybin versus escitalopram on depression symptom severity in patients with moderate-to-severe major depressive disorder: observational 6-month follow-up of a phase 2, double-blind, randomised, controlled trial

EClinicalMedicine September 23, 2024 David Erritzøe, Tommaso Barba, Kyle T. Greenway et al. 46 citations

The Alexander Mosley Charitable Trust and by the founding partners of Imperial College London's Centre for Psychedelic Research.

Assessing expectancy and suggestibility in a trial of escitalopram v. psilocybin for depression.

Psychological Medicine June 1, 2024 Balázs Szigeti, Brandon Weiss, Fernando E. Rosas et al. 74 citations

To investigate the association between pre-trial expectancy, suggestibility, and response to treatment in a trial of escitalopram and investigational drug, COMP360, psilocybin, in the treatment of major depressive disorder (ClinicalTrials.gov registration: NCT03429075). We used data (n = 55) from our recent double-blind, parallel-group, randomized head-to-head comparison trial of escitalopram...

Unique Psychological Mechanisms Underlying Psilocybin Therapy Versus Escitalopram Treatment in the Treatment of Major Depressive Disorder

International Journal of Mental Health and Addiction March 7, 2024 Brandon Weiss, Leor Roseman, Bruna Giribaldi et al. 26 citations

Abstract The mechanisms by which Psilocybin Therapy (PT) improves depression remain an important object of study, with scientists actively exploring acute psychological experiences and neurobiological processes as candidates. In a phase 2, double-blind, randomized, active comparator controlled trial involving patients with moderate-to-severe major depressive disorder, we investigated whether...

Psychiatric risks for worsened mental health after psychedelic use.

J Psychopharmacol March 4, 2024 Alessia Marrocu, Hannes Kettner, Brandon Weiss et al. 51 citations

Background: Resurgent psychedelic research has largely supported the safety and efficacy of psychedelic therapy for the treatment of various psychiatric disorders. As psychedelic use and therapy increase in prevalence, so does the importance of understanding associated risks. Cases of prolonged negative psychological responses to psychedelic therapy seem to be rare; however, studies are limited...

Who are you after psychedelics? A systematic review and a meta-analysis of the magnitude of long-term effects of serotonergic psychedelics on cognition/creativity, emotional processing and personality

Neuroscience & Biobehavioral Reviews February 3, 2024 Ivana Solaja, Kate Haldane, Natasha L. Mason et al. 17 citations

This systematic review and a meta-analysis synthesised the results from contemporary, randomized and non-randomized controlled studies to assess lasting (one week minimum) changes on cognition/creativity, emotional processing and personality from serotonergic psychedelics. PubMed, Embase and PsycInfo were searched in July 2022. Risk of bias was assessed using Rob 2.0 and ROBINS-I. Ten studies...

Personality change in a trial of psilocybin therapy v. escitalopram treatment for depression.

Psychological Medicine 2024 Brandon Weiss, Induni Ginige, Lu Shannon et al. 38 citations

Psilocybin Therapy (PT) is being increasingly studied as a psychiatric intervention. Personality relates to mental health and can be used to probe the nature of PT's therapeutic action. In a phase 2, double-blind, randomized, active comparator controlled trial involving patients with moderate-to-severe major depressive disorder, we compared psilocybin with escitalopram, over a core 6-week trial...

Preliminary evidence for the importance of therapeutic alliance in MDMA-assisted psychotherapy for posttraumatic stress disorder.

European Journal of Psychotraumatology 2024 Richard J. Zeifman, Hannes Kettner, Stephen Ross et al. 34 citations

Background: MDMA-assisted psychotherapy (MDMA-AP) is a combined psychotherapeutic and pharmacologic intervention that shows promise in the treatment of posttraumatic stress disorder (PTSD). Although therapeutic alliance has been established as a key predictor across psychotherapies and is emphasised within MDMA-AP treatment manuals, research has not yet examined the relationship between...

Perceptions of psychedelic personality change, determinants of use, setting and drug moderation: Toward a holistic model

Journal of Psychedelic Studies December 8, 2023 Brandon Weiss, Chelsea Sleep, Nicholas M. Beller et al. 11 citations

Abstract Background Studies have shown evidence for long-term effects of psychedelics on personality, but comprehensive models of psychedelic-mediated personality changes have yet to be explored. Aims The present study aims to investigate (1) perceptions of personality change in the general population, (2) moderators of perceived personality change including setting and drug type, and (3)...

Ayahuasca: A review of historical, pharmacological, and therapeutic aspects.

PCN reports : psychiatry and clinical neurosciences December 1, 2023 Simon Ruffell, Max Crosland-Wood, Rob Palmer et al. 37 citations

Ayahuasca is a psychedelic plant brew originating from the Amazon rainforest. It is formed from two basic components, the Banisteriopsis caapi vine and a plant containing the potent psychedelic dimethyltryptamine (DMT), usually Psychotria viridis. Here we review the history of ayahuasca and describe recent work on its pharmacology, phenomenological responses, and clinical applications. There...

Personality Change in a Trial of Psilocybin Therapy vs Escitalopram Treatment for Depression – CORRIGENDUM

Psychological Medicine July 19, 2023 Brandon Weiss, Induni Ginige, Lu Shannon et al. 1 citation

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Prevalence and therapeutic impact of adverse life event reexperiencing under ceremonial ayahuasca.

Scientific Reports June 9, 2023 Brandon Weiss, Aleksandra Wingert, David Erritzøe et al. 32 citations

The present study examined the safety and efficacy of the ceremonial use of ayahuasca in relation to reports of heightened life event reexperiencing under psychedelics. The study examined (1) the prevalence of specific types of adverse life event reexperiencing, (2) characteristics predictive of reexperiencing, (3) the psychological character of reexperiencing, and (4) the impact of...

A critical evaluation of QIDS-SR-16 using data from a trial of psilocybin therapy versus escitalopram treatment for depression

Journal of Psychopharmacology April 25, 2023 Brandon Weiss, David Erritzøe, Bruna Giribaldi et al. 24 citations

Background: In a recent clinical trial examining the comparative efficacy of psilocybin therapy (PT) versus escitalopram treatment (ET) for major depressive disorder, 14 of 16 major efficacy outcome measures yielded results that favored PT, but the Quick Inventory of Depressive Symptomatology, Self-Report, 16 items (QIDS-SR 16 ) did not. Aims: The present study aims to (1) rationally and...

Examining the Therapeutic Effect of Ceremonial Ayahuasca on Narcissistic Personality and Antagonistic Externalizing in Adults.

Journal of personality disorders April 1, 2023 Brandon Weiss, Chelsea Sleep, Joshua D. Miller et al. 15 citations

Changes in narcissistic traits (e.g., entitlement) following the ceremonial use of ayahuasca were examined across three timepoints (baseline, postretreat, 3-month follow-up) in a sample of 314 adults using self- and informant-report (N = 110) measures. Following ceremonial use of ayahuasca, self-reported changes in narcissism were observed (i.e., decreases in Narcissistic Personality Inventory...

Canalization and plasticity in psychopathology

Neuropharmacology December 27, 2022 Robin Carhart-Harris, Shamil Chandaria, David Erritzøe et al. 106 citations

This theoretical article revives a classical bridging construct, canalization, to describe a new model of a general factor of psychopathology. To achieve this, we have distinguished between two types of plasticity, an early one that we call 'TEMP' for 'Temperature or Entropy Mediated Plasticity', and another, we call 'canalization', which is close to Hebbian plasticity. These two forms of...

Prospective examination of the therapeutic role of psychological flexibility and cognitive reappraisal in the ceremonial use of ayahuasca

Journal of Psychopharmacology March 1, 2022 Gabrielle Agin-Liebes, Richard J. Zeifman, Jason B. Luoma et al. 51 citations

Background: Evidence suggests that psychedelic-assisted therapy carries transdiagnostic efficacy in the treatment of mental health conditions characterized by low mood and the use of avoidance coping strategies. Aims: While preliminary evidence suggests that psychological flexibility and emotion regulation processes play an important role within psychedelic therapy, this prospective study...

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

Frontiers in Psychology November 25, 2021 Brandon Weiss, Victoria Amalie Nygart, Lis Marie Pommerencke et al. 47 citations

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...