Short answer
Early evidence for psilocybin in PTSD is encouraging but limited. In an open-label study of 22 people, a single 25 mg dose of Compass Pathways' synthetic psilocybin reduced PTSD symptom scores by about 30 points on average, and the improvement held through 12 weeks with no serious adverse events. In January 2026, the FDA cleared a late-stage trial. Psilocybin is not approved for PTSD.
Key takeaways
- Only two medications are FDA approved for PTSD, both antidepressants approved decades ago.
- Compass's early study saw CAPS-5 scores fall from 47.5 to about 18 after one dose.
- The study had no placebo group, so a controlled trial is the real test. It's now underway.
- Federal agencies signed a 2026 agreement to speed psychedelic research for veterans.
Why PTSD needs new options
PTSD affects millions of Americans, and treatment options haven't moved much in a long time. Only two medications are FDA approved for it, both antidepressants that were approved decades ago.1 Trauma-focused talk therapies work for many people, but plenty drop out or don't respond. That gap is why psychedelic research for PTSD has drawn so much attention, especially from veterans' groups.
The Compass study
Compass Pathways ran an open-label Phase 2 study of COMP360, its synthetic psilocybin, in 22 people with PTSD at sites in the U.K. and U.S. Each received a single 25 mg dose with psychological support.1
| Measure | Result |
|---|---|
| Average CAPS-5 score at baseline | 47.5 |
| Average reduction at week 4 | 29.9 points |
| Average reduction at week 12 | 29.5 points |
| Serious adverse events | None |
| Most common side effects | Headache (50%), nausea (36%) |
The CAPS-5 is the standard clinician-rated PTSD scale. A drop of roughly 30 points is large. The catch is the design: everyone knew they got psilocybin, and there was no comparison group. That's normal for an early safety study and exactly why the next step matters.
A separate Compass analysis found almost 80% of session time in that study was spent in silence, with monitors providing minimal, non-directive support. The company argues that suggests the drug experience, not intensive therapy, drove the results.2
The late-stage trial
In January 2026, the FDA accepted Compass's application to start a late-stage, Phase 2b/3 trial of psilocybin for PTSD.1 That's the kind of controlled study that can actually establish whether it works. Results are likely years away.
What about MDMA?
MDMA-assisted therapy was the frontrunner for PTSD and reached an FDA decision first, but in 2024 the agency declined to approve it, raising concerns about how the trials were designed and run. Psilocybin and MDMA work in different ways: MDMA mainly floods the brain with serotonin and promotes feelings of safety and connection over a few hours, while psilocybin directly activates serotonin 2A receptors and temporarily reorganizes brain networks.4 Read the full comparison in psilocybin vs. ketamine vs. MDMA.
What veterans should know
On July 13, 2026, HHS and the Department of Veterans Affairs signed a five-year agreement to increase veterans' participation in psychedelic clinical trials, train clinicians, and share safety data, with a strong focus on ibogaine alongside other psychedelics.3 It doesn't make psilocybin available through the VA today. The most direct route for veterans right now is a clinical trial, or a licensed state program in Oregon or Colorado. See our psilocybin therapist finder.
If you're a veteran in crisis, call 988 and press 1 for the Veterans Crisis Line.
Common questions
Is psilocybin better than MDMA for PTSD?
Nobody knows yet. MDMA-assisted therapy had more trial data, but the FDA declined to approve it in 2024, citing concerns about study design. Psilocybin's PTSD data is earlier stage. The two drugs work differently and may suit different people.
Can veterans get psilocybin through the VA?
Not as a standard treatment. The VA funds and participates in research, and a July 2026 agreement between HHS and the VA aims to increase veterans' participation in psychedelic clinical trials. Veterans can also look for trials on ClinicalTrials.gov.
Is psilocybin safe for people with PTSD?
In the early study, there were no serious adverse events, and the most common side effects were headache and nausea. But revisiting trauma can be intensely distressing, which is why research uses trained clinicians, preparation, and follow-up.
Sources
- HealingMaps. FDA clears Compass Pathways to begin late-stage psilocybin trial for PTSD. January 13, 2026. healingmaps.com
- Compass Pathways. Second quarter and first half 2026 financial results and business highlights. August 5, 2026. seekingalpha.com
- U.S. Department of Health and Human Services. HHS, VA partner to advance psychedelic therapies for veterans. July 13, 2026. hhs.gov
- Siegel JS, et al. Psilocybin desynchronizes the human brain. Nature. 2024. doi.org/10.1038/s41586-024-07624-5
This article is for education only and is not medical or legal advice. Psilocybin is a Schedule I substance under U.S. federal law. Talk with a licensed clinician before making decisions about your health. In a crisis, call or text 988.