Criterion 24: Ritual practice

This criterion follows Criterion 23, which builds the physical container, and precedes Criterion 25, which teaches the guiding principles participants carry into the experience. Criterion 24 concerns what the facilitator does to open the container: the ritual acts and spoken invocations that mark the passage from ordinary time into ceremonial time. The module treats ritual as an active ingredient with measurable effects on the experience, states plainly where the evidence for that claim stops, and treats ritual authority as a hazard requiring the same discipline the workbook applies to touch and to scope.

Learning Objectives

By the end of this module, the trainee will be able to:

• Define ritual functionally, as a predefined sequence of formal, repetitive, symbolic acts that lacks direct instrumental purpose, and state what that definition excludes.
• Explain why the ceremonial container is an active ingredient in the experience and not neutral scaffolding around it, citing the placebo and contextual-factors evidence and its limits.
• Describe the predictive-processing account of why context carries unusual weight under a psychedelic, name it as a model, and state what it does and does not establish.
• Report the evidence on music honestly, including the finding that ceremonial elements can work against a participant.
• Mark the seam between what the science reaches and what an invocation claims, and hold both without collapsing one into the other.
• Recognize ritual authority as an amplifier of facilitator power, and apply the authority test to every ceremonial element.
• Apply the cultural authorization standard, and name who authorized any lineage practice they carry.
• Construct and conduct an opening sequence the facilitator can honestly own, with consent and an opt-out built into it.
• Identify the four failure modes of ceremonial ritual: under-ritualized, over-ritualized, mismatched, and coercive.

Key Terms

Ritual. A predefined sequence of formal, repetitive, symbolic actions that lacks a direct instrumental purpose. The definition is deliberately mechanical. It says nothing about whether a ritual is sacred, effective, or true, and it applies equally to an invocation, a surgical time-out, and a pre-flight checklist read aloud.

Invocation. A spoken act at the opening of ceremony that names what is being entered, what is being asked for, and on whose behalf. In many traditions the invocation addresses an agency beyond the participants. In others it addresses only the participants themselves. The distinction matters and is developed below.

Container. The set of conditions, physical, temporal, relational, and symbolic, within which the experience is permitted to unfold. Criterion 23 builds it. Criterion 24 opens it. Criterion 26 holds it.

Liminality. The condition of a person who has left one social state and has not yet arrived at another. Van Gennep and Turner described rites of passage as a sequence of separation, liminal transition, and reincorporation. The ritual opening is the separation, and the ceremony is the liminal phase.

Expectancy. The participant's anticipation of what the experience will be, which measurably shapes what the experience becomes. Expectancy is generated by the facilitator, the setting, the ritual, and the culture, and it is generated whether or not anyone intends it.

Relaxed priors. In the predictive-processing account, the reduced precision weighting of high-level beliefs under a psychedelic, which increases the influence of incoming sensory and contextual information on experience. This is the proposed mechanism by which ritual acquires unusual power during ceremony, and it is a model rather than a settled finding.

Ritual authority. The status a facilitator acquires by being the one who opens the container, speaks the invocation, and defines what the ceremony is. Ritual authority is the mechanism by which every documented category of facilitator boundary violation in this field is made plausible to the person it is done to.

Cultural authorization. A traceable permission, from a living lineage with the standing to grant it, to carry a specific practice. A facilitator either can name who authorized them or cannot. There is no third condition.

The authority test. The question applied to every ceremonial element: does this element make the participant more able to say no, or less?

Core Teaching

What a ritual is, stated mechanically

A ritual is a predefined sequence of formal, repetitive, symbolic acts that lacks a direct instrumental purpose. Every clause of that definition is doing work. Predefined: the sequence exists before this particular ceremony and does not change to suit the facilitator's mood. Formal and repetitive: the acts are performed the same way each time, which is what allows them to be recognized. Symbolic: the acts mean something beyond their physical effect. And lacking direct instrumental purpose: lighting a candle does not illuminate the room in any way a lamp could not, and that is precisely the point. The candle is doing something other than lighting.

Working from that definition rather than from a devotional one has a practical consequence. It lets the facilitator ask what a given ritual act is actually accomplishing, in a person, in a room, under a drug, and to answer without reaching for the vocabulary of the sacred before the mechanical question has been settled. The sacred question is a real question. It is a different question, and it comes second.

The central claim of this criterion is narrow and defensible. Ritual does not act on the compound. It acts on the person who is about to receive the compound, and on the room they receive it in, and its effects are large enough to have been measured.

The container is an active ingredient, and this has been measured

Olson and colleagues (2020) ran a study designed to test how far context alone could carry a psychedelic experience. Thirty-three university students were brought into an elaborately staged environment, an art gallery converted into a simulated psychedelic party, with paintings, projections, ambient music, and confederates posing as participants who visibly and progressively appeared to come up on the drug. The students were told they were receiving a psychedelic. They received an inert placebo. Sixty-one percent reported some drug effect. A subset reported effects in the range that a moderate dose would be expected to produce, and several of those reports were indistinguishable, on the measures used, from what a real dose produces in trial settings.

The study had its limits. The sample was small, drawn from a student population, and unblinded in the sense that everyone believed they were dosed. The design maximized suggestion on purpose, using confederates in a way no clinical trial would. The outcomes were subjective self-report. It was a single site, and the study was not designed to isolate which contextual element carried the effect. What survives all of that is a demonstration, under experimental conditions, that a ceremonial context can produce a drug-like experience in the total absence of a drug.

The consequence for Criterion 24 follows directly. The ritual is one of the agents producing the experience, and treating it as decoration arranged around a pharmacological event mistakes an active ingredient for packaging. A facilitator who opens the container badly has already changed the session that follows, before anyone has swallowed anything.

Why context carries unusual weight under a psychedelic.

The proposed mechanism comes from the predictive-processing account of psychedelic action set out by Carhart-Harris and Friston in their REBUS model (Carhart-Harris & Friston, 2019). The account runs as follows. The brain is understood as continuously generating predictions about the world and updating them against incoming evidence, with each prediction weighted by a precision term that encodes how confident the system is in it. Agonism at 5-HT2A receptors, which are densely expressed on deep-layer cortical pyramidal neurons, is proposed to reduce the precision weighting of high-level priors. The system's confident, top-down models of self and world loosen their grip, and experience becomes correspondingly more governed by what is coming in from below and from around.

If that account is even approximately correct, the implication for ritual is immediate. A person whose own priors have been relaxed will take their priors from somewhere, and the ritual is what is on offer. The invocation, the music, the objects, the facilitator's manner, and whatever the facilitator says about what is happening are all being weighted more heavily than they would be in ordinary consciousness, at exactly the moment the person is least able to evaluate them. This is why the same ceremonial gesture that would be merely pleasant at a dinner party can restructure a person's understanding of their own life in a ceremony.

Now, the caveat: REBUS is a model. It is a productive, partially supported, and contested model, with neuroimaging findings consistent with it and serious critics who read the same findings differently. It is not a settled mechanism, and this workbook does not present it as one. What is better supported than the specific mechanism is the clinical observation the mechanism was built to explain: context and suggestion exert more influence on experience under a psychedelic than off it. A facilitator may act on the clinical observation with confidence. They should describe the mechanism as a model, and should say so if asked.

The best-evidenced ritual element is music, and the evidence includes harm

Music is one ceremonial element in this field with direct empirical study, and the study is worth some analysis, because there are some important considerations here as well. Kaelen and colleagues (2018) interviewed nineteen patients who had undergone psilocybin therapy for treatment-resistant depression, asking specifically about the role of the music. Many described music as central: a carrier that gave the experience shape, a structure that made intense emotion bearable, and something that at times seemed to do the therapeutic work itself. The paper's title, which calls music the hidden therapist, is pulled from that finding.

The same paper demonstrates a polarity in the concept. Some patients experienced the music as intrusive. Some experienced it as directive, pushing an emotional trajectory they did not want and could not escape. Where the music mismatched the participant's state, it was experienced as a demand rather than a support, and in a state where the participant could not simply reach over and turn it off, the mismatch had festered. The evidence base for the single best-studied element of ceremony therefore includes documented instances of that element working against the person it was chosen for.

The study combined qualitative interviews with ratings of participants’ responses to the music and analyses of associations with session experiences and depression outcomes. Its limits include nineteen patients, an open-label treatment study, and no randomized comparison of music conditions (Kaelen et al., 2018). It supports attending to how each participant experiences music; it cannot establish that a particular playlist causes better outcomes. A ceremonial element should be selected with the participant’s preferences and consent, with a way to request changes if it becomes unwelcome.

The seam between the mechanism and the invocation

Invocations are a common encounter across the field. They ask for protection, guidance, the presence of ancestors, the medicine to work gently, and for participants to be held by something larger than themselves. Invocation can produce predictability, mark a transition, regulate arousal, shape expectancy, and give a frightened person the felt sense of being accompanied. The mechanisms above support that claim, as does every hour any facilitator has ever spent in a room. Another common claim is that something is called, and something else answers from an unseen place. That claim lies outside what any measurement in this literature can reach. It is neither disproven nor evidenced, and it belongs to a different order of statement altogether.

The professional obligation is one sentence long. A facilitator may hold either claim, or both, or neither. A facilitator should not present the second claim to a participant as though it were the first. A person whose priors have been relaxed by a serotonergic psychedelic will believe what the person running the ceremony tells them about the nature of reality, and the facilitator who exploits that, even gently, even sincerely, has done something they cannot undo in integration.

Ritual authority is a power amplifier, and this is the safety content of the criterion

The mechanism that makes ritual useful is also the mechanism that can make the ritualist dangerous, and the field has been a bit slow to admit it.

Consider what the facilitator has done by the time the invocation ends. They have defined the boundary of the space, named what is happening inside it, established the vocabulary in which the experience will be interpreted, and positioned themselves as the person who knows what the ceremony is for. They have done this to a room of people whose capacity to evaluate that positioning is about to be pharmacologically reduced for six to eight hours. Ritual authority is a real and measurable asymmetry, and it is at its maximum in exactly the window where the participant's defenses are at their minimum.

Every documented category of facilitator boundary violation in this field passes through that door. Touch that would be recognized instantly as a violation in a clinic is reframed as healing work. Sexual contact is reframed as sacred union, or as what the medicine wanted. Financial demands are reframed as offerings. A participant's objection is reframed as resistance, as ego, as the very thing they came to work on. In every case, ritual supplies the vocabulary that makes the reframing plausible to the person it is being done to. Take the ritual language away and the same acts are simply assaults and thefts.

The discipline that follows is stated as a test, applied to every ceremonial element without exception:

Does this element make the participant more able to say no, or less?

An opening that tells participants what will happen, what they may decline, and how to signal that they want something to stop increases their capacity to refuse. An opening that establishes the facilitator as a conduit for forces the participant cannot see, evaluate, or contradict decreases it. Both are rituals. Both may be sincerely meant. Only one of them is safe, and the tradition an element comes from does not determine which one it is.

A second-order version of the test is useful for the facilitator's own conduct. Any ritual element that increases the facilitator's status, authority, mystique, or unquestionability is a hazard, regardless of what else it does. A facilitator who finds themselves reluctant to give up an element on those grounds should treat the reluctance as information.

Cultural authorization, and the two harms of taking a form you cannot hold

Facilitators routinely perform practices drawn from traditions they have not been trained in and have not been authorized to carry: an icaro half-remembered from a retreat, a smudging sequence learned from a video, a prayer in an idiom the facilitator does not speak. The harm is usually discussed as a harm to the tradition, and it is one. It is also harmful to the participant.

A ceremonial form developed within a living lineage encodes solutions to problems the lineage has addressed for generations: what to do when someone becomes frightened, what to do when someone becomes grandiose, how to close, how to bring a person back. The person authorized to carry the form has been taught those solutions along with it. The person who took the form from a video has the gesture without the knowledge, and the gap between them will open precisely at the moment the form was designed to handle. The participant is the one standing in that gap.

This workbook uses a standard: a single question with two answers. Can you name who authorized you to carry this practice, and would they confirm it? A facilitator who can name that person and that lineage may proceed with fidelity to what they were taught. A facilitator who cannot should build a ritual form they can honestly own. Constructed, secular, and personally authored ritual forms work. The mechanisms above do not require an ancient provenance. They require predictability, meaning, and sincerity, and a competent facilitator can supply all three without hesitation.

The four failure modes

Rituals in ceremony can fail in four recognizable ways. First, the under-ritualized ceremony treats the session as procedural. The room is safe, the dosing is correct, and participants describe afterward a sense that something was missing, that they were processed rather than received. The correction is to add a marked transition, however plain, so the person knows they have entered something. Elaboration is the wrong instinct here, and it is the usual one.

The overly elaborate ceremony is essentially theatrical, with the facilitator as its audience. The participant remains a mere spectator. As the sequence expands, objects increase, invocations prolong, and participants wait. Over-ritualization often reflects a facilitator's attempt to manage their anxiety by demonstrating competence. The solution is to eliminate all elements that do not directly benefit the participant.

The mismatched ceremony uses an idiom that excludes someone in the room. An invocation in a devotional register lands differently on a participant who is an atheist, a practicing Catholic, an observant Muslim, or a person whose religious history is a source of injury. None of those participants is well served by being asked to sit through a form that does not admit them, and few will say so, because the ritual has already established who has standing to object. The correction is to know the room before the room is opened, which means asking during preparation and not during ceremony.

Then, we have the coercive ceremony, which makes an element unrefusable. The participant who does not want to be smudged, who does not want to be touched during the opening, who does not want to speak in the circle, discovers that declining marks them as resistant, closed, or not ready. Consent applies to ritual with the same force it applies to touch. An element a participant cannot decline without paying a social cost is not an element they consented to.

Clinical and Decision Tools

Tool 1. Ritual element inventory, with evidence status and cultural obligation

Each element is assessed on three axes: what it plausibly does, what the evidence actually supports, and what obligation attaches to using it. The evidence status is stated at the level the literature supports and no higher.

Tool 2. The seam. What may be said, and how

Use this before writing any invocation. The left column is the claim, the middle is what a facilitator may assert to a participant as established, and the right is what must be marked as belief or held silently.

Tool 3. The authority test

Applied to every element before it enters the ceremony. A No at any line means the element is modified or removed.

Tool 4. Consent and opt-out protocol for ritual elements

Ritual consent is obtained in preparation, before the compound is administered, and never inside the ceremony. A person in an altered state cannot give reliable consent to anything, which is the same principle that governs touch in Criterion 26.

Tool 5. Cultural authorization decision path

One question, applied honestly, resolves nearly every case.

Tool 6. Opening sequence checklist

Worked Example: An Opening Sequence a Facilitator Can Own

What follows is a complete opening for a group psilocybin ceremony of six participants, with the seam marked throughout and the opt-out stated aloud. The language is written to be said, and it is offered as a model of structure rather than as a script to be recited.

Preparation, three days earlier.

In the preparation session, the facilitator walked each participant through the opening in order: a period of silence, a spoken opening, a round in which each person may say one sentence about why they came, a change of light, and then music. She pointed out which elements could be declined: any participant may pass on the round without explanation, and any participant may ask for the music to change at any time by raising a hand. She asked each participant about their religious background and whether any devotional language would be unwelcome. Two said yes, and one described a childhood in a church she left badly. The facilitator wrote it down and built the opening accordingly, without devotional language of any kind.

The room, before anyone speaks.

Participants are seated. The facilitator has spent ten minutes alone beforehand, steadying herself, because she will be the reference point for six nervous people and she cannot offer a steadiness she does not have. She sits. The room holds silence for perhaps ninety seconds. Nobody explains the silence. The silence is the first act, and it is doing the work of marking that ordinary time has stopped.

The opening, spoken.

"We are going to begin. Before we do, I want to tell you about this next part. Everything we do in the next twenty minutes is here to help you cross from ordinary time into the time of this ceremony. The silence, the light, the music, the round we are about to do. None of it is magic and none of it is required of you. It is a set of signals to your nervous system that something serious has begun, and those signals work, and that is why we use them."

"In a moment I will ask each of you, if you want to, to say one sentence about why you came. If you would rather not, say pass. Pass is a complete answer. Nobody here will think anything of it and neither will I."

"Then I will lower the lights and the music will start. If at any point the music is wrong for you, raise your hand and we will offer alternatives. Doing that tells me something I need to know, and it is welcome."

"The last thing I want to say is this. For the next several hours you are going to be more open to suggestion than you have been in a long time, and I am the person standing here talking. So I am going to be careful with what I tell you, and you should be a little careful about what you accept from me. What I can promise is that we have checked everything that keeps you safe, that I will be here the whole time, and that nothing about you needs to be fixed today. You do not have to go looking for anything. If something comes, meet it. If nothing comes, that is also a real outcome and you have not failed."

The round.

The facilitator goes last, and says only one sentence, and does not make it about herself. One participant passes. The facilitator says nothing about the pass and moves on, which is what makes the pass real.

The transition.

The lights are lowered. The facilitator says one more sentence: that she will be in the room the whole time, that anyone may raise a hand for any reason, and that she is going to stop talking now. The music begins. She stops talking.

What the seam looked like in practice.

Nothing in that opening asserted anything the facilitator could not defend. It said that ritual signals work, which is true. It did not say that anything was being called, or that protection was arriving, or that the medicine had intentions. The facilitator holds beliefs about some of those things. She did not put them into a room full of people who were about to lose the capacity to argue with her.

What was left out, and why.

There was no smudging, because two participants have asthma and one has a history in a religious tradition she left in pain, and the facilitator had asked. There was no invocation of ancestors, because the facilitator has no lineage authorizing her to invoke anyone's ancestors and would not have been able to say who taught her. The opening is plainer than many. It is also entirely hers, and she can stand behind every sentence of it.

Case Vignettes

Work each vignette by identifying the error, the principle at stake, and the correct handling. Then state which tool in this module would have caught it.

Vignette A

A facilitator opens every ceremony with an invocation calling in ancestors, spirit guides, and the protection of the forest. He learned the sequence over two weeks at a retreat in Peru, where he was a guest. He performs it with real sincerity, and participants find it moving. Asked who authorized him to carry it, he says that the medicine authorized him.

Guided questions: What are the two harms here, and which one is this criterion competent to address? What happens to this facilitator's participants at the moment the borrowed form is asked to do the work it was designed for? Is sincerity relevant to the determination? What would an honest alternative sound like?

Vignette B

A facilitator tells participants during the opening that whatever they see in the ceremony is real and true and is the medicine showing them what they need to know. One participant sees, vividly, that her sister betrayed her twenty years ago. She has no waking memory of this. She ends contact with her sister after the retreat.

Guided questions: Which sentence in the opening caused this, and why is it the most dangerous sentence available in a ceremonial context? Connect the harm to the mechanism taught in this module. What could the facilitator have said instead that is both honest and supportive? Where in the seam table does this sentence fall?

Vignette C

A participant does not want to be smudged during the opening. She says nothing, because everyone else is standing in line and the facilitator has just described the smudging as clearing what the participants brought in with them. She submits to it, and spends the first hour of the ceremony angry in a way she cannot account for.

Guided questions: Was consent obtained? What in the framing made refusal costly? At what stage of Tool 4 did this fail? How does the cost of refusal change once an element has been described as necessary?

Vignette D

A facilitator's opening has grown over three years. It now runs forty minutes and includes seven distinct elements, an increasingly elaborate altar, and a long personal account of his own first ceremony. Participants are compliant and complimentary. One assistant notes privately that the participants seem to be waiting.

Guided questions: Which failure mode is this? Whose anxiety is the sequence managing? Apply the fifth line of the authority test to the personal account. What would this facilitator lose by cutting the sequence to ten minutes, and what would the participants gain?

Vignette E

A facilitator plays the same playlist for every ceremony because it has worked well and because the arc is carefully constructed. A participant with a history of sexual trauma finds the swelling emotional section unbearable and cannot say so, because she is four hours into a high dose and the facilitator is across the room with his eyes closed.

Guided questions: What does the Kaelen finding predict here? What was omitted from the preparation session? What signal should have existed and did not? Whose responsibility is it that the participant could not communicate, and what does the answer imply about the facilitator's presence, per Criterion 26?

Role-Play and Practice Scripts

Practice in pairs, then switch. The partner plays a participant. Say the words aloud. A ritual sentence read silently is not practiced.

Marking the seam out loud

During preparation, your partner asks whether the invocation actually protects them. Answer honestly, without being cold or dismissing the question. Practice a version of: "Here is what I know. What we do at the opening genuinely changes how the experience goes, and that is well established. Whether anything is listening, I do not know, and I am not going to tell you I do. Some of the people I trained with believe it. I hold it more loosely than that. What I can promise you is the part I can actually deliver." Notice how hard it is to say this without either overclaiming or deflating the person. Do it three times.

Making a refusal genuinely free

Your partner is a participant who does not want to speak in the opening round. Practice the exact sentence that makes the pass free, and then practice what you do afterward, which is nothing. The most common failure is the facilitator who says "of course, no pressure at all" and then makes warm, extended eye contact, which converts the pass into a cost. Run it until the pass produces no ripple in the room.

Declining to perform a practice you are not authorized to carry

Your partner is a participant who asks whether you will be singing icaros, because the last retreat she attended had them and she found them beautiful. Practice: "I am not going to, and I want to tell you why rather than just say no. I was never trained in that tradition, and the songs are not mine to sing. If I sang them, I would be performing something I do not actually carry, and if you needed what those songs are for, I would not be able to give it to you fully. What I do instead is this, and I can stand behind it." Practice until you can say it without apology and without defensiveness.

Opening a room that includes religious injury

Your partner is a participant who left a religious tradition badly and finds devotional language physically distressing. Practice an opening, aloud, that carries meaning and transition without a single devotional register. Then get feedback: did it still feel like something began?

Cutting your own ceremony

Bring your actual opening sequence. Read it aloud to your partner. Your partner's only job is to ask, after each element, what that element does for the participant. Cut everything that does not survive the question. Notice which cuts you resist, and say aloud why.

Self-Assessment and Reflection

Knowledge check

• Define ritual mechanically and state what the definition deliberately leaves out.
• Describe the Olson et al. (2020) finding, state its limits honestly, and explain what it establishes about the ceremonial container.
• Explain the predictive-processing account of why context carries unusual weight under a psychedelic. Name it as a model and state what is better supported than the mechanism itself.
• State what the Kaelen et al. (2018) study found about music, including the finding that does not flatter the practice.
• Give an example of a sentence a facilitator may say as established, and a sentence that must be marked as belief. Explain the difference.
• State the authority test in one sentence, and apply it to an element of your own opening.
• Explain the two harms of performing a lineage practice without authorization, and identify which one this criterion is competent to address.
• Name the four failure modes of ceremonial ritual and give the correction for each.
• Explain why ritual consent is obtained in preparation and never inside the ceremony, and connect the reasoning to the touch rule in Criterion 26.

Reflection

• Which elements of your current opening did you inherit rather than choose? For each, can you name who authorized you to carry it?
• Read your invocation. Is there any sentence in it that asserts, as fact, something you cannot defend? What would you lose by changing it, and who benefits from that loss?
• Has a participant ever declined an element of your ceremony? If none ever has, consider seriously whether declining is actually available in your room.
• Which part of your opening is doing something for you rather than for the participants? You already know the answer. Write it down.

Summary

Criterion 24 concerns the acts and words with which the facilitator opens the container. Ritual is defined here mechanically, as a predefined sequence of formal, symbolic, non-instrumental acts, so that its function can be examined before its meaning is celebrated. The central claim is that the container is an active ingredient: a ceremonial context can produce a drug-like experience in the total absence of a drug, as demonstrated experimentally by Olson and colleagues in 2020 and never adequately absorbed by this field. The proposed mechanism by which ritual acquires still greater force during ceremony is the relaxation of high-level priors under 5-HT2A agonism, which is a model, is contested, and is named as one, though the clinical observation it was built to explain is on firmer ground than the mechanism itself.

The best-evidenced element is music, and its evidence includes documented harm, which is the corrective this criterion most needs: no ceremonial element is benign by virtue of being traditional or beautiful. Between the mechanism and the invocation runs a seam, and the facilitator's obligation is to know which side of it any given sentence falls on, because a participant under relaxed priors will believe what the person running the ceremony tells them about the nature of reality. From that same fact comes the safety content of the criterion. Ritual authority is a power amplifier, and every documented category of facilitator boundary violation in this field has passed through it. The test applied to every element is whether it makes the participant more able to say no, or less. A form the facilitator cannot name an authorization for is a form they should not perform, because the gap between the gesture and the knowledge will open at exactly the moment the form was designed to close it.

References

Olson, J. A., Suissa-Rocheleau, L., Lifshitz, M., Raz, A., & Veissière, S. P. L. (2020). Tripping on nothing: Placebo psychedelics and contextual factors. Psychopharmacology, 237(5), 1371–1382. https://doi.org/10.1007/s00213-020-05464-5

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

Carhart-Harris, R. L., & Friston, K. J. (2019). REBUS and the anarchic brain: Toward a unified model of the brain action of psychedelics. Pharmacological Reviews, 71(3), 316–344. https://doi.org/10.1124/pr.118.017160

Hartogsohn, I. (2017). Constructing drug effects: A history of set and setting. Drug Science, Policy and Law, 3, Article 2050324516683325. https://doi.org/10.1177/2050324516683325