PTSD

This report summarises what Blossom’s database, supplemented with the primary trial literature, shows about psychedelic treatments for post-traumatic stress disorder (PTSD), and what it does not show. The short version: PTSD is the indication where psychedelic medicine went furthest and then hit its hardest wall. MDMA-assisted therapy produced the most dramatic results in modern psychiatry, two Phase 3 trials in which most participants no longer met PTSD criteria, and then the US regulator looked at the full dossier and declined to approve it. Holding both of those facts at once is the only honest way to read this field.

A note before the evidence

This page is a research summary, not medical advice, and nothing here is a treatment recommendation. None of the psychedelic treatments discussed is approved for PTSD in the United States; ketamine is used off-label, and only Australia permits regulated MDMA prescribing. PTSD is serious and treatable, and decisions about care belong with a qualified clinician. If you are in crisis, contact local emergency services or a crisis line.

On the numbers: Blossom currently tracks 347 papers and 120 trials tagged to PTSD, and those counts appear on this page. The tag is leaky, pulling in general-trauma studies, imaging and biomarker work, comorbid-depression trials and preclinical papers, so the genuinely PTSD-treatment core is smaller than the totals suggest. Read the counts as a measure of database coverage, not as a clean tally of PTSD treatments. Where a key fact sat outside the database, in particular the Phase 3 headline figures and the FDA decision, it has been verified against primary and authoritative external sources and cited as such.

What PTSD is, and why it is hard to treat

PTSD develops in some people after exposure to a traumatic event and combines intrusive re-experiencing, avoidance, hyper-arousal and negative changes in mood and cognition. It is common but not universal after trauma: about 3.9% of people meet criteria in their lifetime, and 5.6% of those exposed to trauma[1]Psychological Medicine, WHO World Mental Health Surveys (2017). First-line care is trauma-focused psychotherapy, which works well but is demanding and has high dropout, alongside two modestly effective antidepressants. That leaves a large group of people who stay ill, which is the unmet need the psychedelic approaches are aiming at.

MDMA-assisted therapy: the strongest evidence in the field

MDMA-assisted therapy is the reason PTSD became psychedelic medicine’s flagship indication. In the first Phase 3 trial (MAPP1), 67% of participants who received MDMA with therapy no longer met diagnostic criteria for PTSD, versus 32% on placebo plus therapy[2]Nature Medicine, MAPP1 Phase 3 (2021). The confirmatory trial (MAPP2) replicated it: 71% of the MDMA group no longer met PTSD criteria versus 48% on placebo, and 46% achieved remission versus 21%[3]Nature Medicine, MAPP2 Phase 3 (2023). A 2026 living meta-analysis of six randomised trials (286 participants) put the effect at a large Hedges’ g of -0.71, with response and remission rates well above control[4]Living systematic review of MDMA-AT for PTSD (2026). A major BMJ review concluded the strongest psychedelic evidence supports MDMA for PTSD[5]BMJ state-of-the-art review (2026).

The mechanism is plausible and partly demonstrated. MDMA reduces fear responses and increases emotional openness, and imaging shows it acutely calms reactivity in the amygdala and subgenual cingulate, the brain’s threat circuitry[6]JAMA Network Open, MDMA affect-circuit RCT (2025). A Phase 3 mediation analysis found the symptom gains were fully explained by increases in self-compassion[7]Eur. J. Psychotraumatology, Phase 3 mediation (2025), suggesting the drug works by enabling the psychological work rather than by acting on symptoms directly. On its own terms, this is the most convincing efficacy story psychedelic medicine has produced.

Why the FDA said no

And yet, in August 2024, the FDA declined to approve MDMA-assisted therapy and asked Lykos Therapeutics to run another Phase 3 trial[8]NPR, FDA declines MDMA therapy (Aug 2024). The agency’s reasoning is the most important thing on this page, because it applies to the whole field. Its concerns centred on functional unblinding, durability and trial conduct[9]AJMC, FDA Complete Response Letter (2024): because MDMA produces unmistakable effects, the great majority of participants and therapists could tell who had received the active drug rather than placebo, which makes the apparent benefit hard to separate from expectancy. Reviewers also flagged high screening-failure rates suggesting an unrepresentative population, and serious allegations of misconduct at one trial site.

This is the crux of the honest reading. The raw numbers are spectacular, but a regulator whose job is to weigh exactly these biases concluded the evidence was not yet trustworthy enough to approve. That is not the same as concluding the treatment does not work; it is a judgement that the existing trials cannot tell the difference between a real drug effect and a powerful expectancy effect. Resolving that ambiguity requires a better-blinded trial, which is precisely what was requested and what does not yet exist.

The unblinding problem, generalised

Functional unblinding is not unique to MDMA, and the data show why it matters. A 2026 analysis of psychedelic trials found that control groups also improve substantially, sometimes more than expected[10]European Psychiatry, control-group response (2026), which is the signature of strong non-specific effects from expectancy and the therapeutic attention built into these protocols. The between-group difference in PTSD trials remained sizeable, but the lesson is that a single-arm or poorly-blinded result can flatter a compound. This is the methodological thread running through every optimistic number below, and the reason early open-label results so often shrink in later blinded trials.

Psilocybin for PTSD: promising but early

Psilocybin is the obvious successor candidate, but for PTSD specifically the evidence is much thinner than for MDMA. The strongest PTSD-primary data is an open-label Phase 2 trial in 22 people, where a single 25 mg dose cut CAPS-5 scores by about 30 points at weeks 4 and 12 with no serious adverse events[11]J. Psychopharmacology, psilocybin PTSD Phase 2 (2025). Encouraging, but open-label and small, so it sits squarely inside the unblinding caveat above.

Most of the rest of the psilocybin trauma signal is indirect, coming from depression trials and naturalistic retreats. Veterans with treatment-resistant depression showed 60% response and 53% remission to a single dose[12]J. Affective Disorders, veterans psilocybin (2025), and a veteran retreat cohort reported a 50% fall in PTSD scores[13]Frontiers in Psychiatry, veteran retreat (2025), but neither was a controlled PTSD trial. A number of randomised PTSD-primary psilocybin studies are now recruiting, including in survivors of sexual assault and intimate-partner violence, so the next few years should produce the controlled data the field currently lacks.

Ketamine: rapid relief, thin PTSD evidence

Ketamine and its approved cousin esketamine act fast and are widely used, but mostly for the depression and suicidality that accompany PTSD rather than for the trauma symptoms themselves. The PTSD-specific evidence is sparse and mixed, and two limits are worth stating plainly: the benefit fades within weeks unless repeated, and a large analysis found that adding structured psychotherapy gave no benefit beyond ketamine alone[14]J. Affective Disorders, ketamine +/- therapy (2025). For PTSD, ketamine is best understood as rapid symptomatic relief, not as a treatment for the underlying disorder.

Ayahuasca, ibogaine and the naturalistic edge

The remaining compounds are at the signal-of-interest stage. For ayahuasca, the PTSD evidence is a mixed-methods case series in which 5 of 7 military veterans showed reliable symptom change maintained at three months[15]Psychological Trauma, ayahuasca veterans case series (2024), with no controlled trial. Ibogaine has drawn attention in veterans with brain injury: in a cohort of 30 veterans given magnesium-ibogaine, the intensity of the mystical experience predicted larger PTSD reductions[16]J. Affective Disorders, magnesium-ibogaine veterans (2026), but again this was a single-arm study. These are hypotheses worth testing, not treatments shown to work.

Beyond classic psychedelics: non-hallucinogenic neuroplastogens

One response to the unblinding problem is to remove the trip altogether. A Phase 2 RCT of TSND-201 (methylone), a neuroplastogen given without psychotherapy, reported a significant CAPS-5 advantage over placebo in 65 participants[17]JAMA Psychiatry, TSND-201 Phase 2 PTSD RCT (2026). If compounds like this can deliver the neuroplastic benefits without a dramatic subjective experience, they would be far easier to blind and to scale. It is early, the trial used an unusual 90% confidence interval, and one result is not a programme, but it points at a route around the central methodological flaw of the psychedelic trials.

The risk side of the ledger

Honesty about benefit requires honesty about harm. Psychedelics are not uniformly safe, and trauma populations are vulnerable. A 2026 survey found that among people reporting a distressing psychedelic experience, 31% met DSM-5 criteria for PTSD[18]Psychological Medicine, distressing-experience survey (2026) (a self-selected sample, so not a population rate, but a real signal). And a review of psychedelic-induced psychosis found long-lasting psychotic symptoms in 3.8% of people with schizophrenia who used them[19]Molecular Psychiatry, psychedelic psychosis review (2024). The supervised, screened trial setting exists precisely to manage these risks, which is part of why unsupervised use is a different and riskier proposition.

Who is developing what

PTSD’s commercial landscape is concentrated and was reshaped by the FDA decision. Lykos Therapeutics, which developed MDMA-assisted therapy, restructured and accepted that a fresh Phase 3 trial is needed[20]FierceBiotech, Lykos fresh Phase 3 (2024), so any US approval is now years away. COMPASS Pathways has opened a PTSD trial of its synthetic psilocybin, academic and Veterans Affairs programmes are running many of the studies, and newer entrants are developing non-hallucinogenic neuroplastogens. Meanwhile Australia, having approved MDMA prescribing for PTSD in 2023[21]Br. J. Pharmacology, Australia down-scheduling (2024), is generating the only regulated real-world experience.

Reading this honestly

So where does PTSD sit? It is both the high-water mark of psychedelic medicine and its sharpest cautionary tale. The MDMA results are the most striking in the field, and they were not enough to win approval, because the trials could not rule out that much of the effect came from people knowing what they had taken. The honest position refuses two easy stories at once: the dismissive one that says none of this works, when the signal is large and consistent, and the breathless one that says PTSD is solved, when the regulator who examined the evidence most closely said no. For people living with PTSD, the most useful and most truthful summary is this: there is genuine, serious science here, the best result the field has produced, and it still has to clear the bar that everything else in medicine has to clear before it can be called a treatment.