Antidepressants and other psychiatric medicines

Reported practice, not a recommendation. This marking applies to everything in this section.

Method note. Metanoia collected these questions and descriptions from public community posts and organization pages on 3 November 2026 (12 items on psychiatric and other medicines). It is one collection in one session. It is not a sample of the field, and the count says nothing about how common anything is. The accounts were not checked against research. Level 3 names a type of source and does not rank its quality. Nothing is quoted and no person or organization is named.

• Does an antidepressant dull the experience? People ask whether long use “ruins” the response. In one community thread, most of the highest-rated replies said that, in their own experience, long use did not stop a deep experience. Forum replies are personal accounts. They say nothing reliable about what is typical or what is safe.
• Weight-loss and diabetes medicines (GLP-1). Guides and clients keep asking whether these medicines weaken or cancel the effect. One reply points to a medical source saying this is not yet known, and raises a guess from animal data about how the 5-HT2A receptor is regulated.
• Medicines a person does not mention. Some commenters guess that a person who felt no effect takes a medicine they did not mention.
• Published lists. Some organizations publish lists of medicine groups in their preparation material, for example for ayahuasca. This card does not reproduce them, because they bear on decisions it does not address.

Posts also ask what to do about a medicine before a session. This card does not address that question.

Most of this research comes from people who took a prescribed medicine under study conditions, and much of it concerns MDMA more than psilocybin. It does not describe what happens outside a research setting. The numbers belong to the studies and are no guide to any person's case. Where the text describes what retreats do, it is reported practice, not a recommendation.

What happens when healthy volunteers take an antidepressant before psilocybin?

• A double-blind, placebo-controlled crossover trial (volunteers tried both conditions, and neither they nor the staff knew which was which) gave 23 healthy volunteers two weeks of escitalopram or placebo before a full psilocybin session in the laboratory. The main outcome, overall intensity of the altered state, did not differ significantly. Source 1, level 1, 2022
• After escitalopram, “anxious ego dissolution” and anxiety were lower (P = 0.03 for each), and so were ratings of bad effect and fear. A sub-scale of difficult, low-point states was lower (P = 0.001). Oceanic boundlessness, positive mood, the total mystical experience score and “good effect” did not differ. Source 1, level 1, 2022
• Peak blood pressure and pupil size were lower after escitalopram. The heart-rhythm interval QTc did not change for the group. The longest value in any participant was 509 milliseconds after escitalopram with psilocybin and 481 after psilocybin alone, and the authors note that relevant lengthening could appear in sensitive people. Escitalopram did not change the way the body handled psilocin. Headache, flashbacks and nausea were about equally common in both conditions. Source 1, level 1, 2022
• Limits named by the authors: one medicine, 14 days only, healthy people, no therapeutic setting, and no correction for multiple comparisons. A company partly funded the study, and one author consults for it. Source 1, level 1, 2022

What about people with depression who were already taking an SSRI?

• An open-label phase 2 study (everyone knew what they were getting) followed 19 people with depression that had not responded to treatment, who had taken one SSRI continuously for at least six weeks. They had one session with psychological support and three weeks of follow-up. 12 of 19 (63.2%) reported some adverse event, none serious, and nobody withdrew. Three had a rise in blood pressure, and the authors say the blood pressure system may not have been calibrated. Source 2, level 1, 2023
• Suicidality ratings did not rise. One participant was sent to an emergency department by a clinician outside the study and was judged by psychiatric assessment not to be at risk. Source 2, level 1, 2023
• Depression scores fell by an average of 14.9 points by week 3 (95% confidence interval 9.2 to 20.7), and 8 of 19 (42.1%) responded or remitted. This was measured in patients with depression and says little about healthy adults. There was no control group, the sample was small and not diverse, and people at high risk of suicide were excluded. A company funded the study. Source 2, level 1, 2023

What about people who came off a medicine before a trial?

These are two post hoc analyses, which means the authors looked back at trial data after it was collected. They describe groups of people. They do not tell a person what to do about a medicine.

• A post hoc analysis of a controlled trial (59 participants, psilocybin versus escitalopram, 56 analyzed) compared 21 people who had come off an antidepressant before entering with 35 who were not taking one. In the psilocybin arm, those who had come off a medicine showed a smaller treatment effect on every measure. Measures of the acute experience did not differ. Depression scores rose in the first group between screening and the start of the trial, which the authors say may be linked to coming off the medicine. Withdrawal symptoms were not measured. Source 3, level 1, 2024
• The authors warn that the analysis was post hoc, the subgroups were small, no group stayed on a medicine, and so no cause can be inferred. The length of the earlier reduction was not recorded. Source 3, level 1, 2024
• A second post hoc analysis, of an open-label trial with a waiting list, looked at 26 people with treatment-resistant depression who had one psilocybin session with psychotherapy. 17 had come off medicines beforehand and 9 had taken none. Over two months there was no significant difference between the groups in depression, anxiety, suicidality or intensity of the experience, and both groups improved. The abstract gives 27 participants and the results give 26, and the paper does not explain the difference. Source 4, level 1, 2025
• Its limits: open label, no placebo, a group of nine, no power to show equivalence, missing data filled by the last observation, and earlier medicines of many kinds. The authors say the result differs from the first analysis and name differences in design and population as possible reasons. Source 4, level 1, 2025
• The two analyses disagree and both are post hoc. Neither is settled.

What do a systematic review and online reports add?

• A systematic review searched PubMed to 21 December 2020 and kept 40 publications of 455 abstracts: 26 controlled trials in healthy people, 3 epidemiological studies and 11 case reports, all about MDMA. Most findings concern MDMA and not psilocybin. Source 5, level 1, 2022
• For psilocybin in healthy volunteers in the laboratory, blocking the 5-HT2A receptor (risperidone, chlorpromazine, buspirone and ketanserin, per the references) reduced the subjective effects. Haloperidol did not change perceptual effects and raised a rating of fear of ego dissolution. Ergotamine had no effect. The one escitalopram trial found no reduction in psychedelic effects (the trial described above). Source 5, level 1, 2022
• The review found only two psilocybin publications from the previous ten years, and none of the psilocybin trials it covered measured physiology (as of December 2020). Source 5, level 1, 2022
• On lithium, the review cites a 2021 analysis of 96 online accounts from Erowid, Shroomery and Reddit. Of 6 reports of lithium with psilocybin, 2 described seizures. Of 10 reports of lamotrigine with psilocybin, none did. Those authors call this low-quality evidence because of missing standardization, selection bias and no clinical verification. This card has not read that analysis itself. Source 5, level 1, 2022
• The reviewers warn that the trials were in young healthy volunteers, usually with one medicine taken once or for 14 days at most, so they are hard to apply to someone who has taken a medicine for months. They say psilocybin has too little interaction data and call for more research. Source 5, level 1, 2022

What do expert guidelines, Oregon rules and retreat surveys say?

• The 2008 Johns Hopkins safety guidelines (expert opinion for laboratory studies) list tricyclic antidepressants and lithium among exclusion criteria, citing a 1996 paper. They note that an acute SSRI and haloperidol strengthen effects in some people while a chronic SSRI and MAOIs reduce sensitivity. The authors call the first group a safety concern and the second a scientific concern. They also list supplements such as 5-HTP and St John's wort among the things to ask about, and, citing a 1998 paper, say that ayahuasca taken with serotonin reuptake inhibitors may cause severe serotonin syndrome. The sources they cite date from the 1980s to 1998, and the guidelines predate trials of psilocybin with an SSRI. Source 6, level 1, 2008
• Oregon's state rules exclude from services people with active suicidal thoughts or psychosis, and people who took lithium in the previous 30 days. Of the four serious events in the 346-person cohort, two participants are recorded at baseline as taking an antidepressant. The paper does not link those events to the medicine and has no analysis of that link. Source 10, level 1, 2026
• In interviews with 49 retreat organizations, 36 (73.5%) asked about prescription medicines, usually on an intake form or in an interview, and 7 more did not ask directly but told people about medicine risks. 7 (14.3%) consulted medical professionals in setting their protocol, and 31 (63.3%) encouraged people to consult a doctor. The authors note that practices on medicines vary widely and call for clear guidelines. The study does not test whether any practice relates to outcomes. Source 11, level 1, 2026

What was measured about benefit?

• Among the studies read for this card, benefit was measured only in patients and healthy volunteers, as described above. In patients taking an SSRI, the depression score fell after one session, with no control group. Source 2, level 1, 2023
• In healthy volunteers, overall intensity and positive mood were unchanged after two weeks of escitalopram, while anxiety and difficult states were lower. Source 1, level 1, 2022
• The two post hoc analyses reached different conclusions, and neither shows cause. Sources 3, 4, level 1, 2024 and 2025
• Metanoia read only the abstracts of a 2023 online survey and a 1996 report that other papers cite as pointing to a dulling effect. Those two sources carry no claim here.

Searches on 3 November 2026 in PubMed, Europe PMC and ClinicalTrials.gov did not locate a study, in people or in animals, that tests whether a GLP-1 medicine changes the subjective effects of psilocybin or another classic psychedelic, or the way the body handles it. The search strings do reach this area, since they returned a mouse study that combined liraglutide and psilocybin, so the wording is unlikely to explain the gap. Metanoia does not state that these medicines dull the experience or that they leave it unchanged.

What was found instead?

• In rats, depleting serotonin weakened the weight loss caused by a GLP-1 agonist within five days, and blocking 5-HT2A (and not 5-HT2C) in the brain weakened weight loss and reduced the drop in food intake. The authors call the data preclinical and preliminary. The direction studied was serotonin shaping the effect of GLP-1 on weight. Whether GLP-1 changes the effect of a psychedelic was not tested. Source 7, level 1, 2017
• In mice, another laboratory found that depleting serotonin did not change the effect of liraglutide, that liraglutide lowered expression of the 5-HT2A receptor gene in the hypothalamus an hour after injection, and that giving a 5-HT2A agonist beforehand weakened the early appetite-lowering effect. The authors say this contradicts the rat study and may reflect a difference between species. Source 8, level 1, 2018
• In obese mice, a single administration of psilocybin neither weakened nor strengthened the weight loss and reduced eating caused by liraglutide, and psilocybin alone had no effect on weight or eating in three obesity models. The question was whether psilocybin adds to weight loss. It was not whether GLP-1 changes the psilocybin experience. The authors note that rodent models may not capture it. Source 9, level 1, 2022

In sum, a link between GLP-1 and the serotonin system has been reported in animals, and results from different laboratories conflict. None of this tests the question people ask. Three further papers (a 2026 mouse study, a review on GLP-1, orexins and psilocybin, and a review in German) were found and not read, so they carry no claim.

“Not located” means that the searches Metanoia ran on 3 November 2026 did not return it. They covered PubMed (17 search strings plus GLP-1 strings), Europe PMC including preprint servers, and ClinicalTrials.gov. More searching could change the picture.

• GLP-1 medicines with psilocybin or another classic psychedelic in people. Not located in PubMed (30 results, none relevant), in Europe PMC (7 preprints and 39 papers from 2025 to 2026) or in ClinicalTrials.gov (no records).
• A controlled trial of long SSRI use. A placebo-controlled trial of an SSRI taken for more than two weeks, in patients or in healthy people, was not located. The one controlled trial read here lasted 14 days in healthy volunteers. A registry record for a trial that would have looked at the length of SSRI use is listed as withdrawn, with no participants.
• A controlled comparison of continuing a medicine with coming off it before psilocybin. Not located. The first analysis above says plainly that this was not tested, and the second says more research is needed.
• Lithium, lamotrigine and other mood stabilizers with psilocybin in a controlled trial. Not located. The only source read is the set of online accounts described above, which its own authors rate as low quality.
• Atypical antipsychotics with psilocybin. Beyond what the review describes about blocking 5-HT2A, no new data were located. Only studies from the 1960s to the 1990s were read.
• People who take several medicines, or have taken one for a very long time. The reviewers say studies in healthy volunteers do not fit this situation.
• Other medicine classes. Medicines for other conditions are outside this card.

This search is a snapshot of one day. If a new study appears, this card is to be re-checked before anything relying on it is used.

Metanoia has not read a first-hand ethnographic source on how modern medicines are handled in Indigenous traditions, so this card makes no claim about what traditions ask or forbid. The 2008 Johns Hopkins authors write that Indigenous cultures limit use to ritual settings with guidance. That is their opinion and not an ethnographic description (6, level 1, 2008). Some organizations in the field publish preparation material that includes lists of medicine groups. That is self-publication by an organization and not a description of a tradition (level 3).

Grade key: 1 = peer-reviewed publication, official document or primary record. 2 = reliable secondary source. 3 = grey source (community, social media, organization pages). 4 = traditional or ethnographic source. A grade names the type of source, and the design and limits are given in the text. "Full text" means Metanoia read the body of the paper in full on 3 November 2026, and any part not read is named. A source read only in part carries no claim on this card. Sources described in the text as found and not read carry no claim and are not listed.

1. Becker AM et al. Acute effects of psilocybin after escitalopram or placebo pretreatment. Clin Pharmacol Ther 2022. DOI 10.1002/cpt.2487 PMID 34743319. Grade 1. Double-blind crossover trial. Full text (supplement not read).
2. Goodwin GM et al. Psilocybin for treatment resistant depression in patients taking a concomitant SSRI medication. Neuropsychopharmacology 2023. DOI 10.1038/s41386-023-01648-7 PMID 37443386. Grade 1. Open-label phase 2 study. Full text (appendix not read).
3. Erritzoe D et al. Effects of discontinuation of serotonergic antidepressants prior to psilocybin therapy versus escitalopram. J Psychopharmacol 2024. DOI 10.1177/02698811241237870 PMID 38520045. Grade 1. Post hoc analysis of a controlled trial. Full text (supplement not read). The section on speculative strategies and on gradual reduction was read and not copied.
4. Chisamore N et al. Comparing Antidepressant Effects of Psilocybin-Assisted Psychotherapy in Individuals That Were Unmedicated at Initial Screening Versus Individuals Discontinuing Medications for Study Participation. Can J Psychiatry 2025. DOI 10.1177/07067437251328316 PMID 40129307. Grade 1. Post hoc analysis of an open-label trial. Full text. The description of the way medicines were reduced was read and not copied.
5. Sarparast A et al. Drug-drug interactions between psychiatric medications and MDMA or psilocybin: a systematic review. Psychopharmacology 2022. DOI 10.1007/s00213-022-06083-y PMID 35253070. Grade 1. Systematic review (PROSPERO CRD42021233519). Full text (case-report appendices not read). It includes a secondary source on online reports.
6. Johnson MW, Richards WA, Griffiths RR. Human hallucinogen research: guidelines for safety. J Psychopharmacol 2008. DOI 10.1177/0269881108093587 PMID 18593734. Grade 1. Expert guidelines, which are opinion and not a trial. Full text. The section on drug treatment in a crisis was read and not copied.
7. Anderberg RH et al. Glucagon-Like Peptide 1 and Its Analogs Act in the Dorsal Raphe and Modulate Central Serotonin to Reduce Appetite and Body Weight. Diabetes 2017. DOI 10.2337/db16-0755 PMID 28057699. Grade 1. Rat study. Full text (supplement not read).
8. Nonogaki K et al. Liraglutide, a GLP-1 Receptor Agonist, Which Decreases Hypothalamic 5-HT2A Receptor Expression, Reduces Appetite and Body Weight Independently of Serotonin Synthesis in Mice. J Diabetes Res 2018. DOI 10.1155/2018/6482958 PMID 29484303. Grade 1. Mouse study. Full text.
9. Fadahunsi N et al. Acute and long-term effects of psilocybin on energy balance and feeding behavior in mice. Transl Psychiatry 2022. DOI 10.1038/s41398-022-02103-9 PMID 35953488. Grade 1. Mouse study. Full text (supplement not read).
10. Korthuis PT et al. Safety and Mental Health Outcomes of Oregon State-Regulated Psilocybin Services. JAMA Netw Open 2026. DOI 10.1001/jamanetworkopen.2026.30608 PMID 42616497. Grade 1. Cohort of 346 participants. Full text (appendices not read).
11. McGuire AL et al. Reported Safety Practices of Publicly Advertised Psychedelic Retreats. JAMA Netw Open 2026. DOI 10.1001/jamanetworkopen.2025.52505 PMID 41499117. Grade 1. Qualitative interviews with 49 organizations. Full text (appendix not read).