The clinical evidence for psilocybin-assisted therapy in depression has matured rapidly over the past decade. The depression topic report on Blossom tracks more than two dozen completed and ongoing trials covering major depressive disorder (MDD), treatment-resistant depression (TRD), and depression with anxiety in cancer patients [1].

Most randomised studies report rapid antidepressant effects within days of a single dose, often sustained for several weeks. The largest published phase 2 study to date dosed 233 participants with TRD across two psilocybin doses (10 mg and 25 mg) versus 1 mg control, with the 25 mg arm showing a meaningful reduction in MADRS at three weeks. The psilocybin compound report summarises the pharmacology, dosing protocols (typically 25 mg in a supported single-session format with preparation and integration), and the safety profile observed across these studies [2].

Key open questions tracked in the topic report: durability beyond 12 weeks, the role of psychotherapy versus drug effect alone, headache and short-term blood pressure changes as the most common adverse events, and how trial designs handle functional unblinding. Phase 3 work is now underway in multiple regions [1][2].

MDMA-assisted therapy combines two or three monitored dosing sessions with a structured course of non-drug psychotherapy (preparation, dosing, and integration). The MDMA compound report describes the receptor pharmacology, including serotonin and norepinephrine release, effects on prosocial neuropeptides, and the therapeutic protocol used across the MAPS-sponsored trials [1].

The PTSD topic report tracks the trial landscape in detail [2]. The MAPP1 (n=90) and MAPP2 (n=104) phase 3 studies both reported clinically meaningful reductions in CAPS-5 scores at the primary endpoint compared with placebo plus therapy, with effect sizes approximately twice those typically observed for SSRIs in PTSD. The first FDA submission was rejected in 2024 with the agency requesting an additional phase 3 trial; that work is now planned. The PTSD report also covers the European regulatory path, which proceeds independently.

Safety data across the phase 3 programme is consistent with the compound's known profile: transient blood-pressure and heart-rate increases during dosing, post-session fatigue, and rare cases of suicidal ideation requiring close monitoring. The protocol's reliance on therapist hours, typically around 40 contact hours per participant, is the dominant cost and access constraint and is discussed at length in both reports [1][2].

Ketamine and psilocybin both produce rapid antidepressant effects but through quite different routes. The ketamine compound report covers the NMDA-receptor antagonist mechanism, the IV racemic protocol (typically 0.5 mg/kg over 40 minutes), and the FDA-approved esketamine (Spravato) intranasal formulation for treatment-resistant depression [1]. Onset is within hours and the effect is measured in days, which is why repeat dosing or maintenance schedules are common.

Psilocybin acts as a 5-HT2A partial agonist and is administered in fewer, longer dosing sessions paired with structured psychotherapy [2]. A single 25 mg dose typically produces an immediate experience lasting 4-6 hours and antidepressant effects measured at three weeks; the durability question (does the effect persist at three months and beyond, and does it require boosters?) is more central for psilocybin than ketamine because the dosing cadence is so different.

The depression topic report contextualises both compounds [3]: ketamine is the more established option (decades of clinical use, FDA-approved derivative, accessible via specialised clinics) and psilocybin is the leading next-generation candidate (phase 3 underway, no approved formulation yet). Direct head-to-head trials are sparse. Most comparisons are between-trial inferences, which the report flags as a methodological caveat.

The Germany country report on Blossom is the most current synthesis of regulatory and research activity in the country [1]. Germany takes both an EU and a national track: the EMA centralised pathway is the primary route for any psychedelic medicine intended for the wider European market, and the BfArM (Federal Institute for Drugs and Medical Devices) handles national clinical-trial authorisation and special-access programmes.

Germany has been an active site for European phase 2 and phase 3 work in MDMA-assisted therapy and psilocybin for depression, with several university hospitals (notably the Central Institute of Mental Health in Mannheim) running studies. The country report tracks academic consortia, sponsor activity, and the state of physician-led training programmes that would be needed for any future rollout of an approved therapy.

For non-medicinal use, Germany's regulatory posture has shifted noticeably with the 2024 cannabis reform, but psilocybin and MDMA remain controlled substances. The report notes that several pilot "compassionate use" pathways have been discussed but not yet enacted, and tracks the political and clinical-society positions that bear on what comes next [1].

The OCD topic report on Blossom collects the small body of clinical work to date [1]. Compared with depression or PTSD, OCD has many fewer randomised psychedelic trials, so the field is at an earlier stage. The most-cited piece of evidence remains a small open-label psilocybin study from 2006 (n=9) showing acute reductions in OCD symptoms during and shortly after dosing, which prompted a slow build-up of follow-up work over the next decade.

More recently, several phase 2 studies have completed or are underway, including investigations of psilocybin for severe, treatment-resistant OCD and proof-of-concept work on DMT and 5-MeO-DMT in related conditions. The topic report tracks the trials register with status, sponsor, and primary endpoints, plus the open-label observations that motivated each programme.

Mechanistically, the rationale for studying serotonergic psychedelics in OCD overlaps with the rationale in depression. Most OCD pharmacotherapy already targets the serotonin system (SSRIs, clomipramine), and evidence of fast-onset 5-HT2A modulation is plausible. The report flags the major caveats: very small sample sizes to date, no positive placebo-controlled phase 3 data, and the structural challenge of running blind trials with a substance whose subjective effects are obvious. It's an active area, not yet an established treatment [1].

Blossom Ask is grounded in Blossom's research database. It does not use general training-data knowledge or the open web. The assistant can search peer-reviewed papers (with structured extracts of arms, baselines, outcomes, and adverse events), clinical trials (status, phase, sponsor, country, results-published flag, and randomisation), editorial topic reports (e.g. depression, OCD, PTSD), compound reports (e.g. psilocybin, MDMA, ketamine, ibogaine), country reports (e.g. Germany, Australia, the United Kingdom), and clinical guidelines.

It works best for synthesis questions that span multiple sources, like:

• "What does the evidence say about X for Y?" It starts with the topic and compound overviews, then checks specific papers.
• "Compare A and B in trials of Z." It pulls both compound or condition reports, plus comparative studies.
• "What's the regulatory environment in country C?" It starts at the country report.
• "Recent phase 3 trials of X." It searches the trials database with filters.

If there's no data on a topic, the assistant says so rather than guess. Claims point back to a Blossom page with a footnote-style citation. These examples show the kind of answer you can expect after signing in.