Ayahuasca and San Pedro ceremonies

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 (10 items on ayahuasca and San Pedro, and a few from neighboring topics). 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.

• How is a first ceremony guided? A person organizing a first ceremony for friends asks how to guide it. Replies describe preparing the place and the music.
• Long preparation guidance. An organization of long standing publishes preparation guidance for ayahuasca that asks people to avoid certain substances and certain foods for a period. It presents the diet as a form of respect for the medicine and for the tradition.
• Screening. An organization states that ayahuasca is not recommended for people with bipolar disorder. People planning a first ceremony ask what to put to a guide in an introductory conversation so that the place is safe.
• One to one or in a group. People ask for a comparison between a private ceremony with one guide and a traditional group retreat, on three points: emotional safety, quality of accompaniment and integration.
• Two substances in one retreat. A retreat notice offers an ayahuasca ceremony followed by a San Pedro ceremony the night after, and presents the pairing as preferred.
• Boundaries during a ceremony. A participant describes a conversation with another participant after a ceremony that felt intrusive. Questions of this kind are taken up on the card on consent, power and boundaries.
• Medicines before a ceremony. People ask about medicines before a ceremony. This card does not address medicines (see "What this card does not say").

Most of this comes from online surveys, interviews with retreat organizations, one small placebo-controlled study and a review. Each source describes who took part, and none gives the rate of any effect among all people who take part in ceremonies. Where the text describes what retreats do, it is reported practice, not a recommendation.

What did a large international survey find?

• An online survey run from 2017 to 2019 in more than 50 countries reached 10,836 people. The sample was not random, took part by choice and looked back on past use. Of these, 8,216 were analysed for physical effects and 7,839 for mental effects. Source 1, level 1, 2022
• Some physical effect was reported by 69.9%. Nausea and vomiting were reported by 62.0%, headache by 17.8% and fainting by 4.1%. Seizures or fits were reported by 1.3%, and the authors do not know whether these were neurological. 2.3% of those who answered the question (132 of 5,775) said they had sought medical care. All of this is self-report. Source 1, level 1, 2022
• Some adverse mental health effect in the weeks or months afterward was reported by 55.4%, and 44.6% reported none. 28.5% said they saw or heard things that others do not, and the authors say some respondents saw this as positive. In no item did more than 4.4% rate the effect as highly severe. For most people who reported effects, they lasted less than a week. Source 1, level 1, 2022
• Among those who reported an adverse mental health effect, 87.6% saw it as part of a positive process of growth or integration (76.3% fully and 11.3% in part), 3.9% did not and 8.6% were not sure. This is self-report and does not show an outcome. Source 1, level 1, 2022
• Compared with use in religious settings (ayahuasca churches), unsupervised use went with more physical effects (odds ratio 1.45). Mental effects went with use in a traditional shamanic context (1.26), a supervised neo-traditional context (1.57) and an unsupervised context (1.71), and with an earlier anxiety disorder (1.26), a physical condition (1.10) and the intensity of the spiritual experience (1.02). An odds ratio above 1 means higher odds than in the comparison group. These are associations. Source 1, level 1, 2022
• The authors list a retrospective online design, selection bias, no measure of how severe or how long the physical effects were, and an unknown composition of the brew. 84% of the religious-context users were Brazilian. They add that the link to context may come from traits of the people who use in each context. Source 1, level 1, 2022

What did studies find about the setting?

• A cross-sectional online survey in Brazil (2,263 people) and the Netherlands (488) gave 2,751 valid answers from adults who had taken part at least half a year earlier, in three contexts: UDV (1,413), neo-shamanic (1,041) and Santo Daime (296). Registered UDV members were invited by email from the organization's office. Source 2, level 1, 2022
• Every dimension of the setting that was measured (social, leadership, decoration, infrastructure, comfort and instructions given beforehand) went with a lower intensity of “challenging experience”, with correlations of 0.21 to 0.36 in size. Four of them (social, comfort, decoration and instructions) together accounted for 41% of the variation in challenging-experience scores. The link with mystical experience was weak, and leadership and comfort accounted for 14% of its variation. The “social” scores were highest among UDV members. Source 2, level 1, 2022
• The authors list a cross-sectional design and self-report, about half the sample having taken part more than 100 times, Santo Daime making up about 10% of the sample, possible inflation of correlations in a large data set, and a music questionnaire that probably missed the live singing used in UDV. Source 2, level 1, 2022

What did a placebo-controlled retreat study find?

• A single-blind field study with a placebo, in which participants did not know which drink they had, took place at six retreats run by one organization in Europe (the Netherlands, Spain and Germany). 30 participants, all experienced (mean 23.7 earlier ceremonies), were assigned at random by the organization to ayahuasca (14) or placebo (16). Measures were taken at baseline and on the morning after. Source 3, level 1, 2021
• Depression and stress (DASS-21) and anxiety (BSI-18) fell in both groups by about the same amount, whatever the drink. The fall in depression tended to be larger in the placebo group (p = 0.053). Only the ayahuasca group showed higher implicit empathic arousal to negative stimuli. The groups did not differ in ego dissolution, and both reported states of low to moderate intensity. Source 3, level 1, 2021
• The authors list very experienced participants (and so expectations), no control by the researchers over set, setting and the preparation of the brew, and no measure of expectations beforehand. Source 3, level 1, 2021

What do retreat organizations report?

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

The items below describe what organizations told interviewers. They are not an operating protocol and not a recommendation, and the study does not test whether any practice relates to outcomes.

• In interviews with representatives of 49 of 298 retreat organizations (July to October 2023, response rate 61.7%), 30 offered ayahuasca, 28 psilocybin, 9 San Pedro and 6 5-MeO-DMT. 34 offered more than one substance and 19 more than one psychedelic. Some combine several substances in one retreat, for example days of ayahuasca followed by days of San Pedro. The authors say the safety implications of such a combination have not been sufficiently studied. Source 4, level 1, 2026
• All 49 collected a medical history. 36 (73.5%) excluded people by condition, most often psychosis (49% of all 49 organizations) and bipolar disorder (32.7%). 21 (42.9%) had worked with a licensed health professional, and 20 (40.8%) said one was present at the retreat. Source 4, level 1, 2026
• 29 (59.2%) said that facilitators use the substance in ceremonies, and 4 of them made clear that a sober person is always present. The authors say it is common, and even considered necessary, in some Indigenous traditions such as Peruvian vegetalismo, and that it marks a gap between a clinical and a traditional point of view. Source 4, level 1, 2026
• The authors list self-report by organizations, English-language only, a Western medical frame that may not fit Indigenous norms, and no test of a link between practices and outcomes. Source 4, level 1, 2026

What is known about San Pedro and mescaline?

• A 2026 systematic review of the use of mescaline for psychiatric disorders (registered in PROSPERO) searched four databases on 27 October 2025 and found 2,770 records. 66 met its criteria (9 case reports, 4 case series, 34 observational studies and 19 trials). Only 10 studies, about 300 people, could go into its statistical analysis. 15 of the 19 trials, mostly from the 1950s, carried a high risk of bias. Source 5, level 1, 2026
• The review reports improvements on scales of depression, well-being, nicotine dependence and alcohol use, and also symptoms such as raised blood pressure, headache, nausea and vomiting. The authors say frequency cannot be determined and the evidence is not sufficient for a clinical decision. Source 5, level 1, 2026
• The review could not tell isolated mescaline, peyote and San Pedro apart. The authors note that a cactus differs from isolated mescaline, because its content varies and it holds other compounds. Source 5, level 1, 2026
• Setting appeared to matter. More well-being was reported in clinical settings and more negative outcomes in reports of unsupervised exposure. The authors warn of reporting bias. Source 5, level 1, 2026
• An online survey in English from January to October 2019 gave 452 valid respondents (83% white, 76% men, 60% from North America, mean age 38). Two thirds (66%) had used San Pedro at some point, 36% peyote and 31% synthetic mescaline. For the most memorable experience, 218 (48%) named San Pedro. Source 6, level 1, 2022
• 60% had used less than once a year. 74% named spiritual exploration or connection with nature as the purpose (8% named healing). 78% reported taking it without the supervision of another person, and 23% reported a “shamanic” guide (more than one answer was allowed). A shamanic guide was more common in the San Pedro and peyote groups (27% and 31%). Source 6, level 1, 2022
• Respondents reported craving (9%), a legal problem (1%) and mental or psychiatric treatment (under 1%). Mystical effects were rated moderate and challenging effects very mild, with no significant difference between types of mescaline. Of those who reported an earlier mental condition, 86% reported improved depression, 80% anxiety and 76% PTSD. This is retrospective self-report, and asking about the most memorable experience tilts it toward the favorable. Source 6, level 1, 2022
• The authors list selection bias, a mostly white and male sample, correlation only, uncontrolled co-used substances, and fewer than 10 respondents from Indigenous communities. Source 6, level 1, 2022

What was measured about benefit?

• No result read for this card shows that a ceremony benefits healthy adults. About half of the respondents in the mescaline survey reported an earlier mental condition, and the placebo-controlled study measured participants only until the morning after. Sources 3, 6, level 1, 2021 and 2022
• In the placebo-controlled study the authors conclude that factors other than the drink can drive improvement, and that there may also be a pharmacological contribution (the empathic arousal), in a small experienced sample. Source 3, level 1, 2021
• Benefit is reported by respondents in the large survey and in the mescaline survey. Neither design can show cause. This was measured in groups who chose to answer, and it is not a promise. Sources 1, 6, level 1, 2022

“Not located” means that the searches Metanoia ran on 3 November 2026 did not return it. They covered PubMed (16 search strings, two of them only to count papers), Europe PMC including preprint servers, and ClinicalTrials.gov. More searching could change the picture.

• Ayahuasca and San Pedro in the same retreat. The one source read describes that it happens and says the safety implications are not sufficiently studied (4). A study of it was not located.
• San Pedro itself. The review could not separate it from peyote and isolated mescaline (5), and the survey is self-report (6). A controlled study of the San Pedro cactus was not located, and no registered trial of it was located.
• Ayahuasca among healthy people outside a medical setting. The controlled study read is small, single-blind and in experienced participants (3). Studies in healthy volunteers from 2024 to 2026 turned up in the searches and were not read, so they could change this picture.
• A primary ethnographic account of UDV or of Shipibo practice. Not located in full text that was open. What this card says about UDV comes from the introduction of a survey paper.
• What happens after a ceremony inside a tradition. One source, the observation of one author on one branch of Santo Daime (8).
• How any of this applies outside a Western frame. The authors of the retreat study say their frame is Western (4).
• Other papers. Several papers on ayahuasca cohorts, on retreats and on single cases were found and not read in full, so this card makes no claim from them.

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

Level 4 names a type of source: interviews with healers and the observation of an author. The papers are peer reviewed. They describe the views of a few healers or of one author, and they do not stand for any tradition as a whole.

Dieta in Peruvian vegetalismo

• A 2021 paper interviewed eight healers in Peru (San Martín region, 2015 to 2017), reached through a therapeutic center in the Amazon. They describe dieta as a technique in which a particular plant is taken together with social isolation, minimal food (no salt, sugar, spice, alcohol or most animal products) and abstaining from sex. They describe uses for physical medicine, for mental healing and for training as a healer (“teacher plants”), and they say the healing is in the dieta. Source 7, level 4, 2021
• The healers stress that dieta does not depend on ayahuasca. In sources the paper cites, diets are more common in remote communities than ayahuasca is. Source 7, level 4, 2021
• Breaking the rules (“crossed diet”) is described as leading to physical or mental reactions that a specialist healer is expected to treat. The healers give their reasons for the rules in terms of digestion and energy. The paper gives no pharmacological explanation, and this card gives none. Source 7, level 4, 2021
• The authors say the physiological action of the dieta is poorly understood, and they warn against turning ayahuasca into an isolated compound. Source 7, level 4, 2021

Santo Daime

• A 2021 paper is a descriptive analysis by one author, drawn from literature, personal observation and informal conversations in one branch of the religion. It is not systematic fieldwork. Santo Daime is a Brazilian religion that took shape in the 1930s in the state of Acre, in the Amazon. It uses a preparation called daime in structured ceremonies (trabalhos) built around hymns (hinos). Some ceremonies follow set dates in the religious calendar. The space is hexagonal, men and women sit on separate sides, and members wear uniforms and use chosen colors and incense. Source 8, level 4, 2021
• Preparation as described: abstaining from sex before and after the ceremony and from alcohol, prayers, and in some cases a diet. Members tend to attend the same church for years and often for life, unlike “free” groups. Source 8, level 4, 2021
• After a ceremony, members stay for hours to talk about the night. An interpretive frame (miração, atuação) reads even a hard experience as healing or purifying. The living conditions people return to vary widely, and the author does not describe them as a formal integration program. Source 8, level 4, 2021
• The author's observation of when it goes wrong: overload, shame and guilt when the order is rigid, inflation of the ego, and a lack of room for non-binary gender identities and for non-Christians. Source 8, level 4, 2021

UDV, Santo Daime and neo-shamanism, as described in a survey paper

• The introduction of a 2022 survey paper, citing other literature, describes UDV and Santo Daime as religions whose members come to weekly or twice-monthly ceremonies. In UDV the doctrine is taught through questions and answers and live singing without instruments (chamadas), in Santo Daime through hymns, and in neo-shamanism through icaros songs and practices such as blowing smoke. The authors say neo-shamanism is more focused on the individual experience. These are descriptions inside a survey paper and not ethnography, and Metanoia did not read the sources they cite. Source 2, level 1, 2022

San Pedro among Indigenous healers in Saraguro, Ecuador

• A 2014 paper interviewed ten Indigenous Kichwa healers (two women and eight men, aged 65 to 80) in 2010 and 2011, together with the Saraguro healers' council and the provincial health department. The group sorts healers into four types, among them the “rikuhampichak”, a visionary healer who uses psychoactive plants in “mesa” ceremonies. Source 9, level 4, 2014
• San Pedro (aguacolla, San Pedrillo) is described as one of the sacred plants healers use most. It is drunk in ceremonies to reach a state in which the healer recognizes the patient's condition and decides on treatment. Vomiting and diarrhea are described as a purification that removes harmful factors, and crying as an emotional release that is spiritual healing. The healers say the response depends on several factors, among them physical and mental constitution and the state of the illness. Source 9, level 4, 2014
• The healers give these aims for mesas with San Pedro: recovery when conventional treatment did not help, getting money, bringing back love, and finding lost animals or objects. There is also external use and use mixed with other plants. Source 9, level 4, 2014
• According to a community leader quoted by the authors, healers gain standing in the community by how well they heal. When a condition cannot be treated by experience, they recommend Western medicine. The authors say knowledge has been worn down by acculturation and that remote communities keep old methods more strictly. The paper has no data on outcomes, safety, frequency or the number of people at ceremonies. Source 9, level 4, 2014

Not read. A primary ethnographic source on UDV, on Shipibo practice and on other Amazonian peoples was not read, so nothing here stands for them. The Native American Church and peyote are outside this card.

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. Bouso JC et al. Adverse effects of ayahuasca: Results from the Global Ayahuasca Survey. PLOS Glob Public Health 2022. DOI 10.1371/journal.pgph.0000438 PMID 36962494. Grade 1. Online survey. Full text (regression tables read in brief).
2. Pontual AAD et al. The influence of ceremonial settings on mystical and challenging experiences occasioned by ayahuasca. Front Psychol 2022. DOI 10.3389/fpsyg.2022.857372 PMID 35911023. Grade 1. Cross-sectional online survey. Full text (figures not seen).
3. Uthaug MV et al. A placebo-controlled study of the effects of ayahuasca, set and setting on mental health of participants in ayahuasca group retreats. Psychopharmacology 2021. DOI 10.1007/s00213-021-05817-8 PMID 33694031. Grade 1. Single-blind field study with placebo. Full text (supplement and figures not seen).
4. 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 (tables read in brief). The paper does not test links between practices and outcomes.
5. Shaw J et al. The ethnopharmacological use of mescaline for psychiatric disorders: a systematic review. Int J Mol Sci 2026. DOI 10.3390/ijms27073081 PMID 41977267. Grade 1. Systematic review. Full text (figures and tables not seen).
6. Uthaug MV et al. The epidemiology of mescaline use: pattern of use, motivations for consumption, and perceived consequences, benefits, and acute and enduring subjective effects. J Psychopharmacol 2022. DOI 10.1177/02698811211013583 PMID 33949246. Grade 1. Online survey. Full text (tables read in brief).
7. O'Shaughnessy DM, Berlowitz I. Amazonian medicine and the psychedelic revival: considering the “dieta”. Front Pharmacol 2021. DOI 10.3389/fphar.2021.639124 PMID 34149407. Grade 4 as source type (ethnographic interviews with eight healers), published in a peer-reviewed journal. Full text.
8. Hartogsohn I. Set and setting in the Santo Daime. Front Pharmacol 2021. DOI 10.3389/fphar.2021.651037 PMID 34017252. Grade 4 as source type (descriptive analysis and personal observation by one author), published in a peer-reviewed journal. Full text (one figure not seen).
9. Armijos C et al. Traditional medicine applied by the Saraguro yachakkuna: a preliminary approach to the use of sacred and psychoactive plant species in the southern region of Ecuador. J Ethnobiol Ethnomed 2014. DOI 10.1186/1746-4269-10-26 PMID 24565054. Grade 4 as source type (ethnographic interviews with ten healers), published in a peer-reviewed journal. Full text.