Short answer
Psilocybin activates serotonin 2A receptors and temporarily reorganizes brain networks, with benefits that can last months after one or two sessions. Ketamine blocks NMDA glutamate receptors, works within hours, but its antidepressant effect usually fades within days to weeks, so it's given repeatedly. MDMA releases serotonin and other chemicals that promote feelings of safety and connection, which may help people process trauma. Ketamine is legal by prescription today. Psilocybin and MDMA are not FDA approved.
Key takeaways
- Psilocybin: serotonin 2A receptor. Lasting effects from one or two sessions. Phase 3 for depression.
- Ketamine: NMDA receptor. Fast but short-lived relief. FDA approved as esketamine (Spravato) since 2019.
- MDMA: serotonin release, plus feelings of trust and safety. Studied for PTSD. FDA declined approval in 2024.
- They're different tools, not competing versions of the same thing.
Side by side
| Psilocybin | Ketamine | MDMA | |
|---|---|---|---|
| Main target | Serotonin 2A receptor | NMDA glutamate receptor | Serotonin release (plus dopamine, norepinephrine) |
| Session length | 4 to 6 hours | About 1 to 2 hours | 4 to 6 hours |
| How often | Once or twice in trials | Repeated, often twice weekly to start | Two or three sessions in trials |
| Best studied for | Depression, including treatment-resistant | Treatment-resistant depression, suicidal ideation | PTSD |
| FDA status (2026) | Application under review | Esketamine approved 2019 | Declined in 2024 |
| Federal schedule | Schedule I | Schedule III | Schedule I |
Psilocybin: the reset
Psilocybin becomes psilocin in the body and activates serotonin 2A receptors, especially in brain regions tied to self-reflection and perception. For a few hours, communication between brain networks becomes looser and more flexible.1 The experience is often emotional and meaningful, and therapy research suggests that meaning may be part of why benefits last.
That durability is psilocybin's standout feature. In Compass's second Phase 3 trial, most patients who responded after two doses still had the benefit six months later.5 Full details in how psilocybin works.
Ketamine: the fast lane
Ketamine works on a completely different chemical system. It blocks NMDA receptors, part of the glutamate system that handles most of the brain's excitatory signaling. That sets off a burst of activity and new connections between neurons. The upside is speed: mood can lift within hours, which is why ketamine is valuable for people in acute crisis.
The downside is that the effect usually fades within days to weeks, so treatment means repeated sessions. Esketamine, sold as Spravato, was approved by the FDA in 2019 for treatment-resistant depression, given as a nasal spray in certified clinics with about two hours of monitoring.2 It's become a big business, with $584 million in global sales in the second quarter of 2026 alone.6
MDMA: the safety signal
MDMA causes neurons to release a flood of serotonin, along with dopamine and norepinephrine, and raises levels of hormones linked to bonding and trust. People typically feel warm, open, and unafraid. In therapy, the idea is that this lowered fear response lets people revisit trauma without being overwhelmed.1
A 2021 Phase 3 trial found MDMA-assisted therapy significantly reduced PTSD symptoms compared with therapy plus placebo.3 But in August 2024, the FDA declined to approve it and asked for another Phase 3 trial, citing concerns about trial design and data.4 MDMA also carries more cardiovascular strain and more misuse potential than psilocybin.
Which one is right?
That's a question for a psychiatrist who knows your history, but the outline looks like this:
- Need relief fast, or need something legal today? Ketamine or esketamine is available now.
- Looking for a lasting shift from a few sessions? That's psilocybin's promise, currently through clinical trials or licensed state programs.
- Trauma and PTSD? MDMA had the most data, but it isn't approved. Psilocybin PTSD trials are underway. See psilocybin for PTSD.
Common questions
Is ketamine a psychedelic?
Ketamine is usually classified as a dissociative anesthetic, not a classic psychedelic. At therapeutic doses it can cause a dreamlike, detached state, which is why it often gets grouped with psychedelics in conversation.
Which works faster for depression, ketamine or psilocybin?
Ketamine can lift mood within hours. Psilocybin's effects often show up within a day or two of a session. The bigger difference is durability: psilocybin's effects have lasted months for many trial participants, while ketamine usually requires repeat treatments.
Can I get ketamine therapy if psilocybin isn't legal where I live?
Yes. Esketamine (Spravato) is FDA approved for treatment-resistant depression and offered at certified clinics nationwide, and many clinics offer off-label IV ketamine. Talk to a psychiatrist about whether it fits.
Sources
- Vollenweider FX, Preller KH. Psychedelic drugs: neurobiology and potential for treatment of psychiatric disorders. Nature Reviews Neuroscience. 2020. doi.org/10.1038/s41583-020-0367-2
- U.S. Food and Drug Administration. FDA approves new nasal spray medication for treatment-resistant depression; available only at a certified doctor's office or clinic. March 5, 2019.
- Mitchell JM, et al. MDMA-assisted therapy for severe PTSD: a randomized, double-blind, placebo-controlled phase 3 study. Nature Medicine. 2021. doi.org/10.1038/s41591-021-01336-3
- Pharmacy Times. FDA declines to approve MDMA for PTSD. August 2024. pharmacytimes.com
- Compass Pathways. Six month data from second Phase 3 trial confirming rapid and durable profile. July 7, 2026. businesswire.com
- The Motley Fool. Forget weight loss drugs: here's another reason to buy Eli Lilly stock. July 29, 2026. via Webull
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.