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Depression

One of the most-studied indications in psychedelic and consciousness research, from antidepressant mechanisms to assisted-therapy trials.

State of the evidence

Synthesized

Synthesized from 25 studies in the library · AI-generated, grounded in the abstracts below

Found by searching the library for Depression, major depressive disorder, MDD, depressive disorder, treatment-resistant depression, then ranked by relevance.

Psilocybin and ketamine/esketamine show rapid and often sustained antidepressant effects in treatment-resistant depression and cancer-related depression, with several randomized trials reporting large improvements within days to weeks. However, the evidence is tempered by small sample sizes, open-label designs in some studies, and mixed durability at longer follow-ups. Mindfulness-based cognitive therapy (MBCT) reduces relapse in recurrent depression, but the evidence for psilocybin and ketamine is still emerging and not yet definitive.

Confidence in the evidence

Moderate
  • Multiple RCTs (e.g., 25610, 25621, 16210, 2362) show consistent positive effects for ketamine and psilocybin, but sample sizes are small (18–79 per arm).
  • Several studies are open-label (16000, 8534, 27749) or have crossover designs, increasing risk of bias.
  • One head-to-head trial (15938) found no significant difference between psilocybin and escitalopram at 6 weeks, introducing some inconsistency.
  • Long-term follow-up data are limited; some studies show sustained effects (16210, 8534), but others (2362) report no sustained response at 12 weeks.
How we rate confidence

Confidence reflects the strength of the underlying evidence, not whether the result is favorable. It weighs the number and size of studies, their design (randomized trials count for more than observational or single-case work), how consistently they point the same way, and their risk of bias.

Tiers run from Insufficient to High. High is rare in this field: small, early, or open-label studies land lower even when their direction is encouraging.

Evidence by study

Direction is each study's finding relative to your question: Supports, Opposes, No effect, Mixed, or Unclear.

Ketamine produced significant improvement in depression within 110 minutes, sustained for 7 days, compared to placebo.

RCT Sample size: 18

High-dose psilocybin produced large decreases in depression and anxiety, sustained at 6 months with about 80% showing clinically significant improvement.

RCT Sample size: 51

Psilocybin produced immediate, substantial, and sustained improvements in anxiety and depression, with 60-80% maintaining clinically significant reductions at 6.5 months.

RCT Sample size: 29

Reviews evidence that ketamine rapidly induces synaptogenesis and reverses stress-related synaptic deficits, supporting a synaptogenic hypothesis of depression treatment.

theoretical

Psilocybin (10 and 25 mg) with psychological support was feasible and associated with reduced depressive symptoms up to 3 months.

open-label trial Sample size: 12

MBCT reduced relapse from 78% to 36% in patients with 3+ previous episodes, but was less effective in those with only 2 episodes.

RCT Sample size: 73

Psilocybin did not show a significant difference in antidepressant effects compared to escitalopram at week 6 on the primary outcome.

RCT

Describes the development of MBCT, a theory-driven intervention incorporating mindfulness training to reduce relapse in recurrent major depression.

theoretical

Psilocybin therapy (20 and 30 mg/70 kg) produced significant antidepressant effects compared to a waiting list control in MDD.

RCT Sample size: 27

Ketamine showed greater improvement than midazolam at 24 hours, with response rates of 64% vs 28%.

RCT Sample size: 73

Describes MBCT as a new approach to preventing relapse in depression.

theoretical

Psilocybin 25 mg significantly reduced MADRS scores at week 3 vs 1 mg control, but sustained response at 12 weeks was not supported.

RCT Sample size: 233

Psilocybin produced large reductions in depressive symptoms at 1 and 5 weeks, with effects remaining significant at 6 months.

open-label trial Sample size: 20

Ketamine significantly improved depressive symptoms within 40 minutes, with effects lasting through day 3.

RCT Sample size: 18

Esketamine nasal spray plus antidepressant showed significantly greater improvement in MADRS score at day 28 compared to antidepressant plus placebo.

RCT Sample size: 227

Trauma re-experiencing occurred during esketamine sessions; in 72.7% episodes resolved, but 27.3% discontinued treatment; favorable outcomes when continued.

retrospective case series Sample size: 22

Psilocybin produced sustained improvements in anxiety, quality of life, and functioning through 12 months, though effects were no longer significant after accounting for depression improvement.

open-label trial Sample size: 15

Ketamine increased morning cortisol 24 hours post-infusion, with a small correlation with decreased suicidal ideation, suggesting enhanced stress-resilience.

RCT

Esketamine users had higher risks of comorbid SUD and, within the esketamine cohort, SUD was associated with higher risks of self-harm, suicide attempt, and hospitalization.

retrospective cohort Sample size: 30670

Esketamine showed faster time-to-response than rTMS over 90 days, but cumulative response rates were similar; suicidal ideation improved more rapidly with esketamine.

retrospective analysis Sample size: 372

Ketamine is associated with favorable effects on subjective sleep quality and preliminary evidence that sleep disturbances may predict antidepressant response.

systematic review Sample size: 1694

Ketamine and esketamine may reduce risk of developing postpartum depression, but data quality was low to very low.

systematic review and network meta-analysis

Ketamine-related neural changes were frequently reported in subcortical regions and default-mode, ventral attention, and visual networks, but results are hypothesis-generating due to heterogeneity.

systematic review

47.1% of patients were anhedonia non-responders to ketamine; non-responders were more likely to be single and had fewer depressive episodes and lower prior substance use disorder.

retrospective analysis Sample size: 34

Therapeutic alliance had indirect effects on depression outcomes via psychedelic experience measures, but direct effects were not significant.

post hoc path analysis Sample size: 79

Points of agreement

  • Both psilocybin and ketamine/esketamine produce rapid antidepressant effects, often within hours to days.
  • Multiple RCTs show that psilocybin and ketamine reduce depression in treatment-resistant populations.
  • Psilocybin's effects are often sustained for weeks to months, with some studies reporting benefits at 6 months.
  • MBCT reduces relapse in recurrent depression, particularly in patients with 3 or more prior episodes.

Conflicts

  • One trial (15938) found no significant difference between psilocybin and escitalopram at 6 weeks, while other trials show large effects for psilocybin vs placebo.
  • Sustained response at 12 weeks was not supported in one psilocybin trial (2362), whereas other studies report sustained effects at 6 months.
  • Esketamine was associated with higher risks of comorbid SUD and adverse outcomes in one retrospective study (28670), contrasting with its overall positive efficacy in RCTs.
  • Anhedonia non-response to ketamine was observed in 47% of patients in one study (28912), indicating variability in response.

Gaps

  • Durability of effects beyond 6-12 months is not well studied for psilocybin and ketamine.
  • Most psilocybin studies have small sample sizes and many are open-label, limiting generalizability.
  • Comparative effectiveness against standard antidepressants is understudied, with only one head-to-head trial (15938).
  • Blinding is challenging in psychedelic trials due to subjective effects, potentially biasing results.
  • Optimal dosing, number of sessions, and long-term safety (e.g., trauma re-experiencing, SUD risks) require further investigation.
  • Mechanisms of action (e.g., neural changes, HPA axis effects) are not fully understood and need harmonized multimodal studies.
Browse these studies in the library
How we analyze this

This synthesis reads the 15 most-cited and 10 most recent studies whose primary subject is Depression, up to 25 in all. The most-cited set anchors the established evidence, and the recent set surfaces work that is too new to have gathered citations yet.

A study qualifies only when Depression or a known alias appears in its title or keywords, so broad reviews that mention it only in passing are left out. Each study is read from its abstract, strongest evidence first, and the summary reports the direction of the results along with any conflicts and gaps.

Latest monthly recap: June 2026 →

5,260 articles · 2,387 from the last two years · 6,846,168 participants across 2,265 studies reporting sample size

Common study designs

review 1063 systematic review 310 experimental study 210 observational cohort 219 randomized controlled trial 536

Simulated States of Consciousness: Inducing Psychedelic Experiences in Virtual Reality

Harman Brar

Virtual reality is used as a therapeutic tool for anxiety, PTSD, and depression through exposure therapy and simulated environments, but its potential to mimic psychedelic experiences has not been examined. Research suggests individuals in VR simulated psychedelic experiences undergo effects similar to those from psychedelic drugs, though the physiological impact on the brain and mind is largely unexplored. To determine whether VR can mimic psychedelics, targeting 5-HT receptor activity in the frontal lobe is proposed as a hypothesis. This paper examines drug mechanisms of psychedelics, the theoretical application of VR-based psychedelic therapy, and postulates a method to measure the effectiveness of psychedelic simulations for psychopathology.

A quantitative exploration of the relationships between regular yoga practice, microdosing psychedelics, wellbeing and personality variables

Stephen Bright, Eyal Gringart, Emily Blatchford et al. preprint

People who microdose psychedelics report similar improvements in psychological wellbeing, openness, and absorption as people who practice yoga. In a survey of 339 adults, both the yoga-only and microdose-only groups scored higher on wellbeing and absorption than a control group. Those who both microdosed and practiced yoga had the lowest depression scores (lower than the microdose-only group) and the lowest anxiety scores (lower than the yoga-only group), and they also had the highest absorption scores. The control group scored significantly lower on openness than all other groups. The findings suggest that microdosing and yoga may have comparable subjective effects and that combining both could be especially beneficial, although the study cannot establish causation.

New insights into the clinical and nonclinical effects of psychedelic substances: an integrative review

Matthias Forstmann, Christina Sagioglou preprint

After a long period of stagnation, research on psychedelic substances like LSD, psilocybin, and DMT has revived over the last decade, with major programs in Europe and the United States. This review summarizes recent insights into their potential for treating mental health disorders, effects on recreational users, and underlying neurological and cognitive processes. It covers the history of psychedelic research, objective and subjective effects, prevalence and correlates of use, and potential for harm. The review examines clinical benefits for major depression, anxiety, and substance use disorders, along with proposed neural and cognitive mechanisms. It also discusses effects on healthy subjects, including psychological wellbeing, personality changes, nature relatedness, and creativity, and concludes with long-term effects of single experiences.

Psychopathological descriptive model of hallucinogenic/psychedelic drugs effect in the treatment of depression and addictions

Nestor Girala

The efficacy of hallucinogenic drugs (ayahuasca, psilocybin, LSD, ketamine) in treating depression and addictions is accompanied by intense emotional states and mystical-type experiences, including feelings of oneness, transcendence, ineffability, and awe. These common psychopathological elements may mediate the drugs' therapeutic action. The paper reviews literature on subjective experiences during such treatments and compares them with other life-changing experiences, discussing the evolutionary value of these emotions for group cohesiveness and the recalibration of cognitions and emotions.

Putative rapid-acting antidepressant nitrous oxide (“laughing gas”) evokes rebound emergence of slow EEG oscillations during which TrkB signaling is induced

Samuel Kohtala, Wiebke Theilmann, Marko Rosenholm et al. preprint

Nitrous oxide (laughing gas), a dissociative anesthetic that blocks NMDA receptors, produces rapid antidepressant effects in animals through a mechanism that emerges after the drug is withdrawn, not during its peak action. The gas induces rebound slow EEG oscillations, a brain state also seen with ketamine and electroconvulsive therapy, that is characterized by sedation and drowsiness. During this withdrawal phase, signaling changes in TrkB and GSK3β proteins gradually appear, suggesting that the antidepressant effect relies on cortical excitability triggered by the drug's offset rather than its acute presence.

Harmaline Attenuates Stress-Induced Depression-Like Behaviour and Biochemical Alterations in Mice

Khush Jain, Fariah Rizwani, Nisarg Sawant et al.

In a mouse model of depression induced by chronic unpredictable mild stress, harmaline, a monoamine oxidase inhibitor from Peganum harmala, reversed depression-like behaviors. Mice given daily oral doses of harmaline (15 mg/kg) for 21 days showed improved performance in behavioral tests and, compared to stressed controls, had lower serum corticosterone and higher brain levels of serotonin, norepinephrine, and dopamine. Harmaline also reduced oxidative stress markers and pro-inflammatory cytokines. These effects were comparable to those of the standard antidepressant imipramine (30 mg/kg). The findings suggest harmaline may mitigate stress-induced depressive disorders by modulating monoamines, oxidative stress, and neuroinflammation.

Combined Ketamine and Psychotherapy Provide No Additional Benefit Beyond Ketamine Alone in Treating Depression or PTSD: Evidence from a Help-Seeking Sample

Tyler Maxwell Moore, Kathryn Walker, Emma Tung et al. preprint

Adding psychotherapy to ketamine treatment does not significantly improve depression or PTSD symptoms more than ketamine alone over 30 days. Both approaches produced substantial, rapid symptom improvement that stabilized after 11-15 days. The study analyzed 202 help-seeking individuals (60% female, mean age 41.3 years) who received either ketamine alone or ketamine plus psychotherapy across six sessions. No significant differences in symptom trajectories emerged between the groups, though exploratory analyses suggested younger females might benefit more from combined treatment and older males from ketamine alone. The findings indicate ketamine's effects may be robust enough that concurrent psychotherapy does not enhance short-term outcomes, but longer-term and demographic-specific effects require further study.

Improvement in Depressive Symptoms in a Patient with Severe and Enduring Anorexia Nervosa and Comorbid Major Depressive Disorder Using Psychotherapy-Assisted IV Ketamine : A Case Report

Amanda Timek, Catherine Daniels-Brady, Stephen Ferrando

A 33-year-old woman with severe and enduring anorexia nervosa and major depressive disorder, who had not improved with numerous prior treatments including antidepressants, mood stabilizers, antipsychotics, electroconvulsive therapy, and various therapies, received seven sessions of intravenous ketamine combined with acceptance and commitment therapy in a hospital setting. She showed increased cognitive flexibility, disappearance of suicidal ideation, and reduction in Beck Depression Inventory scores. Her body mass index was profoundly low at 13, whereas the lowest previously documented in the literature was 16.9. Ketamine-assisted psychotherapy may be a promising treatment for patients with anorexia nervosa and comorbid depression who have failed other interventions.

Publication bias in randomized trials of psilocybin for depression: a Robust Bayesian Meta-Analysis

Çağrı Özkurt preprint

A re-analysis of 12 randomized controlled trials on psilocybin for depression found moderate evidence of publication bias, with a bias-corrected effect size about 41% smaller than originally reported. The original analysis reported a large effect (g = 0.90), but after accounting for selective reporting using Robust Bayesian Meta-Analysis, the effect dropped to about 0.53, with a credible interval that includes zero. This evidence of bias disappeared when open-label studies were excluded, suggesting expectancy-driven effects rather than suppressed negative results. The findings do not overturn the original conclusions but indicate greater uncertainty than previously thought.

Unveiling the Sacred Plant: Reidentifying Soma, Haoma, and the Assyrian Sacred Tree

Milind Raskar

A multidisciplinary investigation combining textual analysis, fieldwork in India's Kutch region, and comparative ethnobotany identifies Vernonia cinerascens Sch. Bip. as a strong candidate for the sacred Soma plant of the Rigveda and its Iranian counterpart Haoma. The plant's woody stems, arrow-like shoots, tawny color, and leafy sprigs match ancient descriptions. Pressing its branches yielded a golden-tawny juice with a crackling sound noted in hymns. Experiential trials reported psychoactive and healing effects—relaxation, enhanced concentration, pain relief, calm joy—similar to those praised in the texts. The plant's known medicinal uses in African ethnobotany for mental disorders and depression further support the identification. Comparisons with Assyrian sacred tree iconography and Zoroastrian Barsom ritual suggest a broader Near Eastern continuity of sacred plant traditions.

Clinical trials

All Depression trials →