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Antidepressants and psychedelics: interactions and risks

How SSRIs and other antidepressants interact with psilocybin, MDMA, ayahuasca and ketamine: blunted effects, serious risks, and what stopping involves.

ReviewedLast updated September 25, 2026

The short answer

Many people interested in psychedelic treatments already take an antidepressant, most often an SSRI or SNRI. That matters in three ways:

  1. Antidepressants can blunt some psychedelics. SSRIs and SNRIs appear to weaken the effects of psilocybin and MDMA.14
  2. Some combinations are dangerous. Ayahuasca contains MAO inhibitors that can interact seriously with antidepressants,6 and lithium may raise seizure risk with psychedelics.7
  3. Ketamine-based treatments work differently. Esketamine is approved for use alongside an SSRI or SNRI, so its approved use doesn’t involve stopping them.8

Molecule by molecule

Molecule With SSRIs or SNRIs: what the research shows
Psilocybin In a survey of 611 reports, people taking SSRIs had about a 47% chance of weaker-than-expected effects.1 Most trials require people to stop antidepressants first, but a small open-label study gave psilocybin to 19 people who stayed on an SSRI.3
MDMA In a lab study, the SSRI citalopram markedly reduced MDMA’s psychological effects.4 The phase 3 PTSD trials required participants to stop psychiatric medications first.5
Ayahuasca Contains MAO inhibitors, which can cause serious drug interactions, including with many antidepressants.6
LSD and other classic psychedelics A review suggests psychedelics may not raise seizure risk on their own, but combining them with some drugs, such as lithium, could.7
Ketamine and esketamine Esketamine is approved in Canada for use with an SSRI or SNRI,8 and its largest head-to-head trial kept everyone on one.9
5-MeO-DMT (BPL-003) A small proof-of-concept study tested it in people with treatment-resistant depression who were taking an SSRI.10

Why SSRIs can blunt psilocybin and MDMA

MDMA works largely by pushing serotonin out through the serotonin transporter, the same site SSRIs block. When researchers gave volunteers the SSRI citalopram before MDMA, most of MDMA’s psychological effects were markedly reduced.4

Psilocybin acts directly on serotonin 2A receptors, so the interaction is less direct. In a survey of people who used psilocybin mushrooms, SSRIs and SNRIs were often linked to weaker effects, and reduced effects were sometimes reported for months after stopping.1 In a controlled study, healthy volunteers took escitalopram for two weeks before psilocybin. It didn’t reduce psilocybin’s positive mood effects, but it did reduce anxiety and other unpleasant effects.2

What stopping an antidepressant involves

Because most psilocybin and MDMA trials require people to stop their antidepressants first, stopping is part of the picture. Two large reviews have measured discontinuation (withdrawal) symptoms:

  • Across 79 studies with about 21,000 people, 31% had at least one discontinuation symptom after stopping an antidepressant, compared with 17% after stopping a placebo. Severe symptoms occurred in about 3%.11
  • A 2025 review of 50 trials found dizziness was the most common symptom, with nausea, vertigo and nervousness also more likely. On average, people had about one extra symptom in the first week.12

These reviews measured withdrawal symptoms, not longer-term outcomes. Any change to antidepressants should only be made with the prescribing doctor.

Where ketamine and esketamine fit

Ketamine and esketamine act on the brain’s glutamate system rather than directly on serotonin. Esketamine was approved to be used together with an oral antidepressant. In Canada, it’s approved for use with an SSRI or SNRI in adults whose depression hasn’t responded to at least two antidepressants.8 In ESCAPE-TRD, all 676 participants stayed on an SSRI or SNRI, and esketamine led to remission in more people than quetiapine.9

So for people who can’t or don’t want to stop their current antidepressant, the evidence and approvals for esketamine are built around staying on it. That’s a practical difference from psilocybin and MDMA, as they’re currently studied.

References

  1. Gukasyan N, et al. Attenuation of psilocybin mushroom effects during and after SSRI/SNRI antidepressant use. Journal of Psychopharmacology. 2023;37(7):707–716. Source
  2. Becker AM, et al. Acute effects of psilocybin after escitalopram or placebo pretreatment in a randomized, double-blind, placebo-controlled, crossover study in healthy subjects. Clinical Pharmacology & Therapeutics. 2022;111(4):886–895. Source
  3. Goodwin GM, et al. Psilocybin for treatment resistant depression in patients taking a concomitant SSRI medication. Neuropsychopharmacology. 2023;48(10):1492–1499. Source
  4. Liechti ME, et al. Acute psychological effects of 3,4-methylenedioxymethamphetamine (MDMA, 'Ecstasy') are attenuated by the serotonin uptake inhibitor citalopram. Neuropsychopharmacology. 2000;22(5):513–521. Source
  5. Mitchell JM, et al. MDMA-assisted therapy for severe PTSD: a randomized, double-blind, placebo-controlled phase 3 study. Nature Medicine. 2021;27(6):1025–1033. Source
  6. Malcolm BJ, Lee KC. Ayahuasca: an ancient sacrament for treatment of contemporary psychiatric illness? Mental Health Clinician. 2017;7(1):39–45. Source
  7. Soto-Angona Ó, et al. Do classic psychedelics increase the risk of seizures? A scoping review. European Neuropsychopharmacology. 2024;85:35–42. Source
  8. Health Canada. Regulatory Decision Summary: Spravato (esketamine). 2020. Source
  9. Reif A, et al. Esketamine nasal spray versus quetiapine for treatment-resistant depression (ESCAPE-TRD). New England Journal of Medicine. 2023;389(14):1298–1309. Source
  10. Seynaeve M, et al. Intranasal 5-MeO-DMT concomitant with SSRI for treatment-resistant depression: a proof-of-concept trial. CNS Drugs. 2026;40(5):725–728. Source
  11. Henssler J, et al. Incidence of antidepressant discontinuation symptoms: a systematic review and meta-analysis. Lancet Psychiatry. 2024;11(7):526–535. Source
  12. Kalfas M, et al. Incidence and nature of antidepressant discontinuation symptoms: a systematic review and meta-analysis. JAMA Psychiatry. 2025;82(9):896–904. Source