In 2016, a team at Johns Hopkins published a survey of 1,993 people about the worst psychedelic experience of their lives. Across all those accounts, only 2.7% had taken the substance with a sober, experienced, trusted guide present in the room. Just 2.1% did so under conditions comparable to a controlled setting (Carbonaro et al., 2016).
That number tells you more about safety in ceremonial medicine than anything else I could offer. Most bad nights don't come from a treacherous medicine. They come from nobody being there.
A San Pedro ceremony is, above all, a structure. A space is opened, held for many hours with song and presence, walked through whatever arises, and closed. This article describes that structure: what happens, in what order, and who is doing what while you are inside it.
It's the second of three. The first covered preparing before you drink. The third covers integrating in the days afterward.
Why I won't describe the experience to you
I could tell you what it feels like. It would be the easiest article to write and the most read. I'm not going to, and I want to explain why.
In the preparation article I pressed one point: intention helps and expectation gets in the way. A text that tells you in advance what you'll see, what you'll feel in the third hour, and what revelation awaits manufactures exactly the expectation you then have to release. I've watched this happen many times. Someone who arrives having read too much spends the night comparing what's happening to what they read, and that comparison pulls them out of the experience.
There's a difference between knowing what will happen and knowing what you'll feel. The first lowers anxiety and lets you arrive settled. The second hands you a script you'll try to follow.
So this is a map of the container, not of the contents.
Opening the sacred space
The ceremony doesn't begin when the medicine is taken. It begins well before, with the opening.
At Dynamis the ceremony is led by Cesar, a paqo of the Q'ero lineage of the Peruvian Andes. The work is organized around the mesa: the arrangement of elements the paqo lays out, which structures the entire night. It holds khuyas, stones worked individually with each person, k'intus of coca leaves offered in threes, the despacho as offering, and the invocation of the Apus and Pachamama. This is a body of practice documented by Peruvian anthropology since the 1955 expedition of the Universidad Nacional San Antonio Abad (Flores Ochoa et al., 2005), and in 2007 the Peruvian state declared it a National Cultural Patrimony.
What happens in that first hour has a function that reads clearly from a clinical angle, even though the language is different. The frame is being established. Who is here, why we came, what is being asked for, what is being offered. When the medicine takes hold, the nervous system will reach for reference points, and those reference points are the ones planted here.
In the Maloca, with seven acres of tropical dry forest around it, that opening happens as the afternoon fades. Each person hands over the written intention they carried in from preparation. That small gesture does something significant: it turns a private purpose into something spoken aloud inside a group.
The shape of the night
Mescaline has its own course, quite different from other medicines. It acts on the 5-HT2A receptor and also on adrenergic and dopaminergic receptors, and its effects stretch across much of a day or a night (Vamvakopoulou et al., 2023).
The approximate arc, per controlled trials (Klaiber et al., 2024) and what's observed in ceremony:
- First phase, roughly the first ninety minutes. Little perceptually and quite a lot bodily: temperature shifts, digestive sensation, sometimes restlessness. This is the stretch where most people wonder whether they took enough.
- Coming up. The effect settles in. Usually the point of greatest nausea, and where anxiety shows up if it's going to.
- The long plateau. The most extended stretch, and where the work happens. It can run for hours.
- Coming down. Gradual rather than abrupt. Many people describe this phase as the clearest and the most useful.
Autonomic effects are real and moderate. In trials with doses from 100 to 800 mg, systolic blood pressure stayed below 180 mmHg in every participant, all of them healthy people screened beforehand (Klaiber et al., 2024). Screening is what makes that figure applicable, which is why it takes up so much room in the previous article.
During the plateau there isn't much talking. There's no agenda of activities. It sounds strange to say, but a good portion of a ceremony consists of lying on a mat while something rearranges itself inside you.
The song, which is not background music
Here is one of the most elegant findings in recent psychedelic research.
Kaelen and colleagues interviewed 19 patients with treatment-resistant depression treated with psilocybin and analyzed how the music shaped what happened to them. The result: their experience of the music predicted the reduction in depression one week later. The overall intensity of the drug effect did not (Kaelen et al., 2018). Patients described the music as a source of guidance and as something that carried them when the experience turned difficult.
The paper is titled "the hidden therapist." That strikes me as an exact description of what the paqo's song does.
Healers never needed a clinical trial to know this. The song doesn't accompany the ceremony. It leads it. When someone gets lost, the voice is the thread they follow back.
There's a difference between what Imperial College studied and what happens in the Maloca. They used a recorded playlist, designed to track the curve of the drug effect. In ceremony the song is live and responds to what is happening in the room at that moment. A paqo who sees someone struggling can change what he sings. A recording can't do that.
Purging
This is the question I get most often, and almost always with anticipated embarrassment.
Vomiting during a wachuma ceremony is common. It has a clear physiological basis: nausea is a documented effect of mescaline, and it increases with dose (Klaiber et al., 2024). It also carries a reading within the traditions that work with master plants, where purging is understood as a release rather than an accident.
Fotiou and Gearin (2019) documented in their ethnographic work that purging is understood as a considerably broader category than vomiting: it includes yawning, trembling, sweating, and crying, all read as ways of releasing loads. That research concerns ayahuasca in the Amazon, not wachuma in the Andes, and I don't want to map one tradition onto another. What it does show is that the frame of purging as release runs across several plant traditions, and it helps explain why nobody in ceremony apologizes for vomiting.
This is why each person has a bucket beside them from the start. Its being there, in plain sight, communicates something before anyone uses it: this is expected, this is accounted for, you won't be interrupting anything.
When it gets difficult
This is the section that matters, and where the data are clearer than most people assume.
Back to the Johns Hopkins survey. Nearly two thousand people describing their worst experience. Of them, 10.7% reported putting themselves or others at risk of physical harm. But the analysis identified what reduced that probability, and it wasn't dose or prior experience:
- Physical comfort and safety of the setting reduced the likelihood of risky behavior (OR = 0.562).
- Social support during the session reduced it as well (OR = 0.657).
- Having a guide present was associated with a shorter difficult experience, not a less intense one.
And the finding that reorganizes everything: the difficulty of the experience was positively associated with the personal meaning people later attributed to it (r = 0.41), while the duration of that difficulty was negatively associated with meaning and with subsequent well-being. The authors conclude that intervention during a challenging experience should aim at shortening its duration rather than suppressing its intensity (Carbonaro et al., 2016).
That describes precisely the work of whoever holds the space. It isn't preventing the night from getting hard. It's keeping the person from getting stuck there.
The same study found that 84% of those people, speaking about their worst experience, said they had benefited from it. A difficult night is not a wasted night. A difficult night with nobody to shorten it can be.
In clinical terms, what a competent sitter does when someone panics is co-regulation. Porges (2011) described neuroception as the process by which the body assesses the safety of an environment before the mind gets involved. A dysregulated nervous system reads a calm nervous system and begins organizing around that reference. This is why it matters so much who is in the room, and why it matters that the person isn't frightened.
In practice: move closer, lower your voice, offer physical contact only if the person wants it, remind them where they are and that this has an ending. Sometimes walk them outside for a while. It rarely takes more than that. What you don't do is leave them alone to sort it out.
When what surfaces is heavy personal material, that's where my role begins. Not during the ceremony, which is the paqo's territory, but afterward, in the integrative psychology work that follows.
Who stays awake
The most widely cited safety guidelines in the field recommend at least two people monitoring throughout the session, and that those people have built a relationship of trust with the participant before it begins (Johnson, Richards, & Griffiths, 2008). That isn't an administrative detail. Two people allow one to accompany whoever needs it without leaving the rest of the group uncovered.
When you're evaluating a space, this is the question I would ask before any other: who stays awake all night, how many of them, and what training do they have. A serious space answers that without discomfort and with concrete numbers. If the answer is vague, you've already learned something important.
Worth asking too: what happens if someone needs the bathroom mid-effect (the right answer involves being accompanied), what happens if someone wants to leave the room, whether there's a protocol for a medical emergency and how far the nearest clinic is, and what happens the following morning.
Nobody drives that night or the next morning. This is why the cabins sit on the same land and why the structure of the retreat folds the following day into the program.
The closing, and the first hours
The ceremony is closed explicitly. It doesn't dissolve because people drifted off to sleep: there's a moment when the space that was opened gets closed, with the same intention that opened it.
Then food is shared. Soft fruit, bread, tea. That gesture looks minor and isn't. Eating together after many hours of silence is the oldest way we have of returning to the shared world.
The first hours often bring a particular clarity, and also fatigue. It's common to want to talk a great deal or not at all, and both are fine. What I don't recommend is making important decisions that day, or announcing to anyone the conclusions you reached during the night. You don't yet know which ones will hold.
That's what the third article in this series is about. What you do in the following weeks determines how much of the ceremony becomes actual change, and it's the most neglected part of the whole process.
Frequently asked questions
How long does a San Pedro ceremony last?
Mescaline's effects extend across much of a day or night, considerably longer than other medicines. The ceremony itself runs from the opening in the late afternoon through the closing, and you should also keep the entire following day free of commitments.
What happens if I get frightened or panic?
It's a real possibility and it's accounted for. Someone comes to you and stays with you, and the work is to shorten that stretch rather than suppress it. The research is clear that a sitter's presence is associated with shorter difficult experiences, and that brevity matters more than intensity for what remains afterward.
Will I vomit?
It's common but not universal. Nausea is a documented effect of mescaline and increases with dose. In ceremony it's understood as part of the work rather than a problem, and each person has a container beside them from the start.
Can I leave the ceremony if I want to?
You can move, step outside for air, use the bathroom, always accompanied. What isn't a good idea is leaving the property mid-effect, which is why ceremonies are held where you stay the night.
Can I take part if I've never done anything like this?
Yes. Many people arrive with no prior experience. What matters isn't your history but that you've gone through screening and preparation, and that you trust the people who will hold the space.
What makes the difference
Back to the 2.7% from the opening, because it sums everything up. Among people who had a bad time, almost none had a trained, sober person holding the space.
That means most of what people fear about these medicines isn't a risk of the medicine. It's a risk of the context. And context is the one part of this whole equation that can be controlled completely.
A well-held ceremony doesn't guarantee you a pleasant night. None does, and I distrust anyone who promises that. What it does guarantee is that whatever happens, you won't be alone inside it.
If you'd like to talk about whether this is your moment: write to us and let's set up a preliminary conversation. Always start there, never with a booking.
You can also see how our plant medicine retreat is structured and upcoming dates in Tamarindo, Guanacaste.
References
Carbonaro, T. M., Bradstreet, M. P., Barrett, F. S., MacLean, K. A., Jesse, R., Johnson, M. W., & Griffiths, R. R. (2016). Survey study of challenging experiences after ingesting psilocybin mushrooms: Acute and enduring positive and negative consequences. Journal of Psychopharmacology, 30(12), 1268-1278. https://doi.org/10.1177/0269881116662634
Flores Ochoa, J. A., Núñez del Prado B., J. V., & Castillo Farfán, M. (Eds.). (2005). Q'ero, el último ayllu inka: Homenaje a Óscar Núñez del Prado y a la expedición científica de la UNSAAC a la nación Q'ero en 1955 (2nd ed.). Fondo Editorial de la Facultad de Ciencias Sociales, UNMSM; Instituto Nacional de Cultura.
Fotiou, E., & Gearin, A. K. (2019). Purging and the body in the therapeutic use of ayahuasca. Social Science & Medicine, 239, 112532. https://doi.org/10.1016/j.socscimed.2019.112532
Johnson, M. W., Richards, W. A., & Griffiths, R. R. (2008). Human hallucinogen research: Guidelines for safety. Journal of Psychopharmacology, 22(6), 603-620. https://doi.org/10.1177/0269881108093587
Kaelen, M., Giribaldi, B., Raine, J., Evans, L., Timmermann, C., Rodriguez, N., Roseman, L., Feilding, A., Nutt, D., & Carhart-Harris, R. (2018). The hidden therapist: Evidence for a central role of music in psychedelic therapy. Psychopharmacology, 235(2), 505-519. https://doi.org/10.1007/s00213-017-4820-5
Klaiber, A., Humbert-Droz, M., Ley, L., Schmid, Y., & Liechti, M. E. (2024). Safety pharmacology of acute mescaline administration in healthy participants. British Journal of Clinical Pharmacology. https://doi.org/10.1111/bcp.16349
Porges, S. W. (2011). The polyvagal theory: Neurophysiological foundations of emotions, attachment, communication, and self-regulation. W. W. Norton.
Vamvakopoulou, I. A., Narine, K. A. D., Campbell, I., Dyck, J. R. B., & Nutt, D. J. (2023). Mescaline: The forgotten psychedelic. Neuropharmacology, 222, 109294. https://doi.org/10.1016/j.neuropharm.2022.109294
