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Journal articleGoodwin GM, Aaronson ST, Alvarez O, et al., 2026, , J Affect Disord, Vol: 406
INTRODUCTION: The contribution of patient support to psilocybin's antidepressant effects remains uncertain. METHODS: Relationships between therapeutic alliance (Scale to Assess Therapeutic Relationship-Patient version; STAR-P), psychedelic experience (Five-Dimensional Altered States of Consciousness Questionnaire and Emotional Breakthrough Inventory; 5D-ASC and EBI) and clinical outcomes (Montgomery-Åsberg Depression Rating Scale; MADRS) were explored using correlation and path analysis for individuals with treatment-resistant depression receiving 25 mg psilocybin with monitoring and support (N = 79). RESULTS: Change from Baseline to Week 3 MADRS scores showed weaker correlations with pre-dosing therapeutic alliance (-0.178) than with measures of the psychedelic experience: EBI (-0.637), Oceanic Boundlessness (-0.508), and Visual Restructuralization (-0.516). Path analysis showed no nominally significant direct effects of therapeutic alliance on Week 3 MADRS scores, but there were nominally significant effects of therapeutic alliance on psychedelic experience (Oceanic Boundlessness (β = 0.28), Visual Restructuralization (β = 0.27), and Auditory Alterations (β = 0.25)). Only one indirect effect of therapeutic alliance on clinical outcome reached nominal significance (via Visual Restructuralization; β = -0.15). Stronger effects were seen on clinical outcomes for psychedelic experience (EBI (β = -0.59), Oceanic Boundlessness (β = -0.53), Visual Restructuralization (β = -0.54), and Auditory Alterations (β = -0.24)). CONCLUSIONS: The therapeutic alliance appeared to facilitate the psychedelic experience, and these experiences in turn had stronger nominally significant direct effects on clinical outcomes. The effects of the alliance itself on therapeutic efficacy were either limited or absent. TRIAL REGISTRATION: EudraCT number: 2017
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Journal articleAday JS, Carhart-Harris RL, Boehnke KF, 2026, , Am J Geriatr Psychiatry, Vol: 34, Pages: 873-876
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Journal articleCarhart-Harris R, 2026,
Human brain changes after first psilocybin use
, Nature Communications, ISSN: 2041-1723Psychedelics have robust effects on acute brain function and long-term behavior but whether they also cause enduring functional and anatomical brain changes is largely unknown. In an exploratory, placebo-controlled, within-subjects, electroencephalography (EEG), and magnetic resonance imaging (MRI) study in 28 healthy, entirely psychedelic-naive participants, anatomical and functional brain changes are detected from one-hour to one-month after a single high-dose (25 mg) of psilocybin. Increases in cognitive flexibility, psychological insight, and well-being are seen at one-month. Diffusion tensor imaging (DTI) done before and one-month after 25mg psilocybin reveals decreased axial diffusivity bilaterally in prefrontal-subcortical tracts that correlate with decreases in brain network modularity (fMRI) over the same month. Enduring functional brain changes are largely absent, but network modularity change (numerical decrease) negatively correlates with well-being change (significant increase), in line with previous findings in depression. Increased cortical signal entropy (EEG) at 1- and 2-hours post-dosing predicts improved psychological well-being at one-month. Next-day psychological insight mediates the entropy to well-being relationship. All effects are exclusive to 25mg psilocybin; no effects occur with a 1mg psilocybin placebo.
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Journal articleAli SS, Carhart-Harris RL, Sieg KG, 2026, , Nature Mental Health, Vol: 4, Pages: 540-550
Obsessive–compulsive disorder (OCD) is a psychiatric condition with high rates of treatment resistance. Emerging neuroimaging evidence implicates dysfunction in large-scale brain networks, particularly the cortico–striatal–thalamo–cortical (CSTC) circuit, default mode network (DMN) and salience network (SN). Lysergic acid diethylamide (LSD) and psilocybin induce acute dysregulation of the DMN and increase connectivity across normally segregated networks, potentially disrupting maladaptive rumination and self-referential loops. Furthermore, psychedelics may improve aberrant DMN–SN connectivity in OCD, improving functioning under the triple network model. Simultaneously, both LSD and psilocybin modulate CSTC function, particularly by modulating activity in the subthalamic nucleus and striatum, regions implicated in compulsive behavior. Beyond network disruption, psychedelics rapidly enhance neuroplasticity via 5-HT<inf>2A</inf>-receptor-mediated pathways, promoting dendritic spine formation (rodents). These dual mechanisms may ‘reset’ pathological patterns and support long-term restructuring of maladaptive circuits. Future clinical trials with specific neuroimaging endpoints are needed to validate the presented framework for psychedelic action in OCD.
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Journal articleGirn M, Doss MK, Roseman L, et al., 2026, , Nat Med, Vol: 32, Pages: 1543-1554
Psychedelic drugs are re-emerging as promising scientific and clinical tools. However, despite a rapidly expanding literature on their therapeutic value, the neural mechanisms underlying psychedelic effects remain unclear. Resting-state functional magnetic resonance imaging studies of acute psychedelic effects, conducted independently by several research groups, have so far yielded fragmented and sometimes inconsistent findings. Here, to help facilitate greater convergence, we conducted a 'mega-analysis' integrating 11 independent resting-state functional magnetic resonance imaging datasets across five psychedelic drugs (psilocybin, lysergic acid diethylamide, mescaline, N,N-dimethyltryptamine and ayahuasca) from research groups spanning three continents and five countries. By applying a uniform preprocessing pipeline and a Bayesian hierarchical modeling framework, we discovered several common features in the induced alterations to brain function across drugs and sites. Most prominently, we identified a core signature of increased functional connectivity between transmodal (default, frontoparietal and limbic) and unimodal networks (visual and somatomotor), with subnetwork specificity. Furthermore, key subcortical regions (thalamus, caudate and putamen) and the cerebellum exhibited altered coupling with sensorimotor networks. In contrast to several single-site reports, Bayesian modeling revealed weak-to-moderate and selective reductions in within-network functional connectivity, with substantial variability across drugs and networks. Together, these findings extend past work by demonstrating that psychedelics reconfigure large-scale cortical organization while selectively engaging subcortical circuitry. This study provides the most comprehensive synthesis of psychedelic brain action to date, helping resolve inconsistencies and offering a probabilistic map of how psychedelics alter large-scale brain organization. We hereby provide a cornerstone to benchmark and shephe
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Journal articleNewson M, Roseman L, Haslam SA, 2026, , Discov Ment Health
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Journal articleAgnorelli C, Peill J, Sawicka G, et al., 2026, , J Cereb Blood Flow Metab
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 resting-state fMRI (intrinsic brain activity, functional connectivity), before and after ketamine. While group-level analyses showed no significant increases in PET synaptic markers, ketamine administration resulted in significantly elevated glutamate levels within the anterior cingulate cortex (ACC). Functional connectivity analyses revealed reduced coupling between the ACC and the dorsolateral prefrontal cortex (dlPFC) and increased coupling between the ACC and the amygdala in the days following ketamine administration. Our multimodal analysis revealed that participants showing an increase in [11C]-UCBJ volume distribution (VT), a putative index of synaptic plasticity, showed a correlated reduction in intrinsic activity within regions belonging to the default mode network (DMN). By linking molecular, cellular and network-level changes, our results point to the DMN as a central hub where ketamine may reshape brain hierarchies in the long term, providing new directions for understanding its therapeutic mechanisms and developing targeted treatments.
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Journal articleAgnorelli C, Garling HD, Paterson LM, et al., 2026, , J Cereb Blood Flow Metab
Serotonin (5-hydroxytryptamine, 5-HT) is a neuromodulator underpinning various psychological and physiological processes, with dysregulation implicated in numerous psychiatric disorders. Non-invasive measurement of endogenous 5-HT release in the living human brain is essential to advance understanding of the serotonergic system. The combination of Positron Emission Tomography (PET) neuroimaging of serotonergic receptors with pharmacological and behavioural challenges that stimulate endogenous 5-HT release, offers a unique approach to quantify 5-HT dynamics in vivo. In 2010, Paterson and colleagues concluded in a thorough review that measures of 5-HT release were constrained by limitations in the sensitivity of available tracers and potency of pharmacological challenges. Novel tracers combined with optimised pharmacological challenge paradigms have demonstrated sensitivity to changes in endogenous 5-HT, enabling reproducible detection of acute 5-HT release in both preclinical and human studies in the last 15 years of research. These include the use of agonist radioligands with preferential binding to high-affinity receptor states, such as [11C]AZ10419369 and [11C]Cimbi-36, antagonist tracers, such as [18F]Altanserin, refined challenge designs using pharmacological 5-HT releasers, such as fenfluramine and amphetamine, and the integration of hybrid PET/MR imaging to assess neurovascular aspects. These advances have shifted the field from questioning feasibility to addressing optimal strategies for measuring serotonergic dynamics.
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Journal articleRibeiro D, Hallett W, Howes O, et al., 2026, , EJNMMI Phys, Vol: 13, ISSN: 2197-7364
INTRODUCTION: Positron Emission Tomography (PET) imaging is a close ally of Precision Medicine, and it has been proven to be indispensable in the field of Psychiatry. This imaging modality may also present an important role in understanding Neurodevelopmental disorders and their link to Psychiatric conditions, with new highly selective binders being used currently in research. PET imaging requires the administration of radiopharmaceuticals, where the radioisotope is in incorporated into a highly selective binder. Dosimetry and injected activity optimisation play a crucial role in the field of PET imaging as they allow to determine the radiation dose absorbed by target and non-target tissues, and determine the lowest amount required to deliver images with diagnostic quality and obtain reliable quantitative data, without overexposing patients. The aim of this research is to investigate the feasibility of reducing the injected activity of the [11C]-(+)-PHNO and [11C]UCB-J radiopharmaceuticals, for patients with neurodevelopmental disorders who undergo brain imaging in the PET-Magnetic Resonance (MR) scanner, without compromising quantitative accuracy of outcome measures. RESULTS: No statistically significant differences were found when comparing the 1/2 to 1/6 datasets with the full injected activity [11C]-(+)-PHNO dataset. Furthermore, the findings obtained from investigating the impact of low injected activity administrations of [11C]UCB-J revealed that it is possible to reduce the administered activity by 1/2, when the clinical outcome measure under evaluation is the binding potential relative to non-displaceable volume (BPND). When the outcome measure under investigation is the standard uptake volume ratio (SUVR), it is possible to decrease the injected activity to 1/3, for [11C]UCB-J. CONCLUSIONS: The simulation and analysis methodologies deployed in this project are suitable for investigating scans with low injected activity for tracers with cortical and striatal
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Journal articleFabiano N, Stubbs B, Lawrence DW, et al., 2026, , Discov Ment Health, Vol: 6
Upwards of 50% of people do not respond to the primary treatment modalities for major depressive disorder (MDD), which has led to increased attention and use of alternative methods, including exercise and psychedelics. While interventions using either exercise or psychedelics have demonstrated largely positive results in isolation, their synergistic potential has yet to be explored. As such, this commentary provides an overview of exercise/psychedelics as a treatment for depression and their potential synergy and/or complementarity. From a biological perspective, psychedelics acutely enhance brain-derived neurotrophic factor (BDNF) signalling, while exercise provides sustained BDNF elevation; psychedelics enhance neuroplasticity largely in the cortex (with only modest effects in the hippocampus), while exercise boosts hippocampal neurogenesis; psychedelics increase glutamate release via stimulation of 5-HT2A receptors on pyramidal neurons, while exercise enhances glutamatergic transmission via the endocannabinoid system and reduction of systemic inflammation; both boost serotonin release; and psychedelics temporarily disrupt functional connectivity between the hippocampus and default mode network (DMN), while exercise normalizes this connectivity, which may sustain post-psychedelic gains. Through the lens of psychological and behaviour change, psychedelics appear to facilitate the adoption or maintenance of physical activity habits, increase psychological flexibility, and since exercise is associated with emotional resilience to acute stress, this may allow users to experience deeper immersion and exploration during their psychedelic experience, improving antidepressant outcomes. In summary, exercise and psychedelics have numerous potential complementary mechanisms, therefore, future research is warranted to explore the efficacy, tolerability, safety, and neurobiology of this combination.
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