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, randomized clinical trial to evaluate the efficacy and safety of intravenous DMT (SPL026; DMT fumarate) in adults with moderate-to-severe MDD. Participants received a single 21.5-mg dose of DMT or placebo infused over 10 min, along with supportive psychotherapeutic support, followed by a 2-week assessment. A subsequent open-label phase offered all participants a second DMT dose. The primary outcome was the change in Montgomery-Åsberg Depression Rating Scale (MADRS) at 2 weeks. Secondary outcomes included response (≥50% reduction in MADRS score) and remission (MADRS ≤ 10). A total of 34 participants were randomized, 17 to placebo-active and 17 to active-active. At 2 weeks, the DMT group showed a significantly greater reduction in MADRS score than placebo (mean difference = -7.35; 95% CI = -13.62 to -1.08; P = 0.023). In the open-label phase, AD effects persisted up to 3 months, with no significant differences between those who received one versus two doses. Adverse events were mostly mild to moderate, commonly infusion site pain, nausea and transient anxiety. No serious adverse events occurred. A single dose of DMT with psychotherapeutic support produced a rapid, significant reduction in depressive symptoms, sustained up to 3 months. The treatment was well-tolerated and safe. ClinicalTrials.gov registration: NCT04673383 .

Abstract Psychedelics 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 25 mg 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 25 mg psilocybin; no effects occur with a 1 mg psilocybin placebo.

Background3,4-Methylenedioxymethamphetamine (MDMA) is associated with distinctive prosocial and empathogenic effects, yet the consistency and scope of its impact on social functioning in humans remain unclear. Although numerous placebo-controlled studies have examined MDMA’s acute social effects, findings vary widely across subjective and behavioural domains.MethodsWe conducted a systematic review of placebo-controlled studies investigating the acute effects of MDMA on social functioning in adults. Outcomes included self-reported social and emotional experience, task-based measures of social cognition and behaviour, and relevant physiological and neurobiological indices. Studies administering MDMA as the sole intervention were included.ResultsAcross 76 studies, MDMA reliably enhanced subjective social experience, including feelings of sociability, emotional openness, closeness, and emotional empathy. In contrast, behavioural manifestations of prosociality, such as cooperation and trust in economic or performance-based tasks, were inconsistent and strongly context dependent. A convergent finding across behavioural, physiological, and neuroimaging measures was reduced processing of social threat, including diminished sensitivity to negative social cues and impaired recognition of fear and anger.ConclusionsMDMA consistently alters how social interactions are experienced, but subjective changes do not reliably translate into observable prosocial behaviour. Its most robust social effects are the modulation of social threat processing rather than a general enhancement of prosocial action. These findings help explain the divergence between felt and enacted social effects of MDMA and highlight the importance of context and measurement in interpreting laboratory outcomes. Clarifying these mechanisms has implications for understanding MDMA’s therapeutic potential in conditions characterised by heightened social threat and avoidance.

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.

Rationale: Major depressive disorder (MDD) shows marked sex differences in prevalence, symptomatology, and treatment response. However, women remain underrepresented in many clinical trials, and sex-specific treatment outcomes are rarely examined. Objectives This study reanalyzed data from a randomized controlled trial comparing psilocybin and escitalopram for MDD to evaluate sex differences across multiple psychological domains. Methods We reanalyzed data from a six-week, double-blind randomized controlled trial comparing psilocybin with escitalopram in adults with moderate-to-severe MDD. Post-treatment depressive symptoms (MADRS, QIDS-SR-16, BDI), anhedonia (SHAPS), anxiety (STAI), thought suppression (WBSI), and well-being (WEMWBS) were modeled as a function of sex, treatment condition, their interaction, and baseline symptom severity. Sexual dysfunction severity (PRSexDQ-SALSEX), assessed only at the six-week follow-up, was analyzed separately as an ordinal outcome. Results Sex-related patterns emerged for anxiety and anhedonia. Women receiving psilocybin showed greater reductions in anxiety than men (STAI: 95% CrI − 17.5 to − 3.29), whereas women receiving escitalopram showed greater reductions in anhedonia than men (SHAPS: 95% CrI − 4.63 to 0.00). For the remaining continuous outcomes, sex differences were generally small and uncertain. Sexual dysfunction severity was lower overall in the psilocybin group than in the escitalopram group and lower in women than in men, although the treatment-by-sex interaction was not significant. Conclusions This reanalysis identified domain-specific sex-related patterns in anxiety and anhedonia, suggesting that responses to psilocybin and escitalopram may differ between women and men. These preliminary findings support adequately powered, sex-balanced, and hormone-informed trials of serotonergic treatments for MDD.

Background: Multi-criteria decision analysis (MCDA) has been used to quantify drug harms in the United Kingdom, the European Union, Australia, and New Zealand. This paper presents the result of an MCDA conducted in Canada, with the aim of informing Canadian drug policy and contributing to public understanding of drugs' relative harms.Methods: A panel composed of 20 experts from six provinces determined 16 drugs to evaluate on 16 dimensions of harm (ten representing harm to people who use the drug; six representing harm to others). At a two-day decision conference, the panel scored each drug on a scale of 0-100 for each harm criterion, then weighted the relative importance of each criterion.Results: This analysis of drug harms in Canada found that alcohol causes the most harm overall, with a cumulative weighted score of 79. It was followed by tobacco (45), nonprescription opioids (33), cocaine (19), methamphetamine (19), and cannabis (15). The finding that alcohol causes the most harm is consistent with the results of previous MCDA drug harm studies.Conclusion: These harm scores express population-level harm rather than individual-level "harmfulness." They reflect not only a drug's pharmacological risk profile but also the current policy context in Canada. The high score for alcohol underscores a failure to adopt policies to address alcohol-related harms, despite the known health harms and the existence of proven policy measures. More broadly, when developing drug policies, governments should consider the harm-both individual and societal-caused by drugs and by the laws and regulations that govern them.

Background Medicinal cannabis (MC) became legalised in Australia in 2016, yet relatively little is known about its longer-term effectiveness within the Australian context. Methods P2021 Australia was a prospective observational cohort study that collected data on patients prescribed MC (from as Product Formulary) for four conditions: chronic pain, anxiety, post-traumatic stress disorder (PTSD) and multiple sclerosis (MS) via validated questionnaires (baseline then 3-monthly for up to 12 months). Results At study end, a total of 522 patients had enrolled: 221 (42.3%) reported their primary complaint was chronic pain, 222 (42.5%) anxiety, 53 (10.2%) PTSD and 26 (5%) other conditions. Three-month data for chronic pain, anxiety and PTSD indicate MC is effective at reducing primary symptoms as well as improving quality of life (QoL), sleep, mood/depression and perceived overall health (insufficient data for MS). In chronic pain patients, effect sizes (Cohen's d ) at 3 months were 0.75 for pain severity and 0.8 for pain interference (BPI questionnaire), for anxiety patients, 1.34(GAD-7 questionnaire) and for PTSD patients 1.44 (PTSD Checklist-Civilian Version), and there were also significant improvements across other measures, including QoL, perceived overall health, mood/depression and sleep, with effect sizes ranging from 0.54 to 1.15. Twelve-month data for chronic pain and anxiety patients indicates that MC use is associated with improvements in primary symptoms, QoL, perceived overall health, mood/depression and sleep quality (insufficient data for PTSD and MS). Conclusion MC may be a useful treatment option for conditions, including chronic pain, anxiety and PTSD, where other treatments have not been successful.

OBJECTIVE:Psilocybin is an emerging intervention for depression that may be at least as effective as selective serotonin reuptake inhibitors (SSRIs), but effects of the two treatments on the neural correlates of emotional processing have never been directly compared. METHODS:The authors assessed neural responses to emotional faces using blood-oxygen-level-dependent (BOLD) functional MRI (fMRI) in two groups with major depression. One group (N=25; 9 women and 16 men) received two dosing sessions with 25 mg psilocybin plus 6 weeks of daily inert placebo, and the second group (N=21; 6 women and 15 men) received 6 weeks of escitalopram plus two dosing sessions with a nonpsychoactive (placebo) dose of 1 mg psilocybin. Both groups had equal psychological support throughout: 3 hours of preparation, one in-person integration session following the psilocybin dosing sessions, and two further integration sessions conducted via video call or telephone. An emotional face fMRI paradigm was completed before treatment and at the 6-week posttreatment primary end point (3 weeks following psilocybin dosing sessions). RESULTS:Patient group (psilocybin versus escitalopram) interacted with time point (before versus after treatment) on a distributed set of cortical regions. Post hoc within-condition analyses showed that posttreatment BOLD responses to emotional faces of all types were significantly reduced in the escitalopram group, with no change or a slight increase in the psilocybin group. Analyses of amygdala responsivity showed a reduction of response to fearful faces in the escitalopram group, but lesser effects for the psilocybin group. CONCLUSIONS:Despite large improvements in depressive symptoms in the psilocybin group, psilocybin therapy had only a minor effect on brain responsiveness to emotional stimuli. These results are consistent with prior findings that the antidepressant action of SSRIs is often accompanied by a reduction in emotional responsiveness, but this effect may not occur in psychedelic therapy.

The past 50 years have seen remarkable advances in the science of medicine. The pharmacological treatments of disorders such as hypertension, immune disorders, and cancer are fundamentally different from those used in the 1970s, and are now more often based on disorder-specific pathologies. The same cannot be said for psychiatric medicines: despite remarkable advances in neuroscience, very few innovative treatments have been developed in this field since the 1970s. For depression, schizophrenia, anxiety disorders, and ADHD, pharmacological classes of medicines discovered through serendipity in the 1950s are still used despite hundreds of billions of US dollars being spent on drug discovery attempts based on new neuroscience targets. This Personal View presents my opinion on the reasons innovation in psychiatric treatment has not progressed as well as in other disorders. As a researcher in the field, I offer suggestions as to how this situation must be rectified soon, as by most analyses mental illness is becoming a major health burden globally. Most of my evidence is referenced, but where I have unpublished knowledge gained from consulting with pharmaceutical companies, it is presented as an opinion.

Determining the scale of neural representations is a central challenge in neuroscience. While localized representations have traditionally dominated, evidence suggests information is also encoded in distributed, hierarchical networks. Recent research indicates that the hierarchy of causal influences shaping functional patterns serves as a signature of distinct brain states, with implications for neuropsychiatric disorders. Here, we first explore how whole-brain models, guided by the thermodynamics of mind framework, estimate brain hierarchy and how perturbing such models enables the study of in-silico transitions represented by static functional connectivity. We then apply this to major depressive disorder, where different brain hierarchical reconfigurations emerge following psilocybin and escitalopram treatments. We build resting-state whole-brain models of depressed patients before and after interventions and conduct a dynamic sensitivity analysis to explore brain states' susceptibility-measuring their capacity to change-and their drivability to healthier states. We show that susceptibility is on average reduced by escitalopram and increased by psilocybin, and that both treatments promote healthier transitions. These results align with the post-treatment window of plasticity opened by serotonergic psychedelics and the similar clinical efficacy of both drugs in trials. Overall, this work demonstrates how whole-brain models of brain hierarchy can inform in-silico neurostimulation protocols for neuropsychiatric disorders.

Disorders of consciousness (DoC), including unresponsive wakefulness syndrome (UWS) and minimally conscious state (MCS), have limited treatment options and are characterized by low complexity of brain activity. Recent research suggests that psychedelic drugs, which enhance the complexity of brain activity, could offer promising therapies. Here, individualized whole-brain computational models are developed for patients with DoC, optimized with empirical functional magnetic resonance imaging data and diffusion-weighted imaging data, upon which the administration of lysergic acid diethylamide (LSD) and psilocybin is simulated. An in silico perturbation protocol is applied to assess brain dynamics, first distinguishing between different states of consciousness, including DoC, anesthesia, and the psychedelic state. Then, brain dynamics are assessed before and after a simulation of psychedelic drugs on patients with DoC. Findings indicated that the simulation of LSD and psilocybin shifted the brain activity of patients with DoC closer to criticality (the point at a phase transition between order and chaos), with a greater effect in patients in the MCS. In patients with UWS, the treatment response correlated with structural connectivity, while in patients in the MCS, it aligned with baseline functional connectivity. These results offer a computational foundation for using psychedelics in DoC treatment and highlight the potential future role of computational modeling in drug discovery and personalized medicine.

Neuroplasticity, the ability of the nervous system to adapt throughout an organism's lifespan, offers potential as both a biomarker and treatment target for neuropsychiatric conditions. Psychedelics, a burgeoning category of drugs, are increasingly prominent in psychiatric research, prompting inquiries into their mechanisms of action. Distinguishing themselves from traditional medications, psychedelics demonstrate rapid and enduring therapeutic effects after a single or few administrations, believed to stem from their neuroplasticity-enhancing properties. This review examines how classic psychedelics (e.g., LSD, psilocybin, N,N-DMT) and non-classic psychedelics (e.g., ketamine, MDMA) influence neuroplasticity. Drawing from preclinical and clinical studies, we explore the molecular, structural, and functional changes triggered by these agents. Animal studies suggest psychedelics induce heightened sensitivity of the nervous system to environmental stimuli (meta-plasticity), re-opening developmental windows for long-term structural changes (hyper-plasticity), with implications for mood and behavior. Translating these findings to humans faces challenges due to limitations in current imaging techniques. Nonetheless, promising new directions for human research are emerging, including the employment of novel positron-emission tomography (PET) radioligands, non-invasive brain stimulation methods, and multimodal approaches. By elucidating the interplay between psychedelics and neuroplasticity, this review informs the development of targeted interventions for neuropsychiatric disorders and advances understanding of psychedelics' therapeutic potential.

[This corrects the article DOI: 10.7759/cureus.78171.].

Recent clinical trial data suggests that ratings on depression scales are lowered after psilocybin therapy compared to placebo, though it is unclear what neuropsychological mechanisms underpin these effects. This study compared psilocybin, with an established antidepressant, escitalopram, to investigate whether there are shared or distinct effects on emotional information processing. Patients with long-standing moderate-to-severe depression were randomly and double-blindly assigned in a 1:1 ratio to receive either 1) two doses of 25 mg of psilocybin, 3-weeks apart, plus 6-weeks of daily placebo (psilocybin group N = 30); or 2) two doses of 1 mg of psilocybin 3-weeks apart plus 6-weeks of daily oral escitalopram (escitalopram group N = 29); all patients received the same psychological support. Behavioural measures of affective bias as well as subjective measures of depression were collected at baseline and at the primary 6-week endpoint, using an established computerised task (Facial Emotion Recognition Task) and Quick Inventory of Depressive Symptomatology, respectively. Change in affective bias was further correlated with change in depression scores measured concurrently as well as at 1-month post-trial follow-up (week-10), corrected for baseline depression severity. Negative bias in facial expression recognition decreased after both treatments to a comparable level. Concurrently, change in negative affective bias was not associated with change in depression. Longitudinally, a decrease in the misclassification of positive faces as negative was associated with a decrease in depression scores at week-10 for the escitalopram group only. Therefore, a more positive behavioural bias in emotional processing was seen following psilocybin and citalopram compared to baseline. This highlights the potential for at least some overlap in cognitive mechanisms across two distinct treatments, which is noteworthy given the short dosing regimen with psilocybin.