The Good Friday Experiment: Psilocybin at Marsh Chapel

This is the Good Friday Experiment, often called the Marsh Chapel Experiment, and it is still cited as the founding study of research into psychedelics and mystical experience. We tell it from the sources: what was measured, what people reported, and what stayed missing from the record for almost thirty years.

A physician who wanted to be a theologian

Walter Pahnke was 31 when he planned the study. He was a medical doctor and an ordained minister, and he was writing a Harvard doctorate in the program on Religion and Society. One of his main academic mentors was a psychologist whose name would soon stand for something else entirely: Timothy Leary. Since 1960 Leary had been running the Harvard Psilocybin Project, a series of studies with the compound that the chemist Albert Hofmann at Sandoz in Basel had isolated from Mexican mushrooms a few years earlier.

Pahnke was not interested in intoxication. He was interested in an old question from the history of religion: is there an experience that mystics of every era and tradition share, and can it be measured? As his yardstick he took a book published in 1960, Mysticism and Philosophy by the philosopher Walter T. Stace. Stace had compared the reports of Christian, Islamic and Eastern mystics and distilled their common features. Pahnke turned them into a typology with nine categories: unity, both inner and outer; transcendence of time and space; a deeply felt positive mood; a sense of sacredness; the noetic quality, the certainty of having encountered something real; paradoxicality; ineffability; transiency; and lasting positive changes in attitude and behavior afterwards.

The idea was bold, and for its time methodologically careful. Instead of asking whether someone felt enlightened, he would place people double-blind in a religious setting and score their reports against these features. According to the later follow-up, Pahnke himself took no psychedelic substance before the study was finished. He did not want to be biased.

Timeline

• 1960: Stace publishes Mysticism and Philosophy; Leary's psilocybin project starts at Harvard.
• April 20, 1962: the experiment at Marsh Chapel.
• 1963: Pahnke's dissertation, Drugs and Mysticism, is accepted; Leary's time at Harvard ends the same year.
• 1966: Time magazine reports that all the psilocybin students had a mystical experience.
• July 10, 1971: Pahnke dies at 40 in a scuba diving accident off the coast of Maine.
• 1986 to 1989: Rick Doblin tracks down 19 of the 20 participants and interviews 16.
• 1991: Doblin's follow-up is published.
• 2006: Roland Griffiths at Johns Hopkins publishes the modern version of the question.
• May 2025: after years of dispute, the study of clergy from several world religions appears.

Double-blind in the pews

The volunteers came through Walter Houston Clark, who taught psychology of religion at Andover Newton Theological School. Twenty Protestant divinity students, none of whom had ever taken a comparable substance. Howard Thurman, dean of Marsh Chapel at Boston University and one of the best-known American preachers of his time, the man whose theology had shaped Martin Luther King Jr., provided the rooms: several small meeting rooms and a private chapel in the basement. Upstairs Thurman led his congregation through Good Friday; downstairs the participants listened over speakers.

Pahnke divided the twenty into five groups of four. Each group had two guides, ten assistants in all. The groups met beforehand for two hours to build trust. The guides were told not to talk about mysticism, so that nobody would know which experiences were expected. Decades later the participants confirmed that this was respected. One remembered that nobody had handed them Stace or Jakob Boehme to read, and that they had not been steered in that direction at all.

The real trick was the placebo. Pahnke did not give the control group sugar. He gave them nicotinic acid, a B vitamin that acts faster than psilocybin and produces a warm flush of the skin. Whoever took it felt something. That was supposed to keep the control group from knowing right away that they had drawn the blank, and in the first half hour some of them did believe they had received the real thing.

One deviation was pushed through by Timothy Leary against Pahnke's wishes: the guides also took a capsule, one per group the active drug, the other a placebo. Leary argued it would create fellowship and give the students a sense of safety. Pahnke feared that critics would later hold it against him as a source of bias. The guides filled out no questionnaires, and their experiences were not recorded.

Two and a half hours in the basement

The nicotinic acid kicked in and then wore off. The psilocybin came on later and kept building. At some point during the service it became obvious to everyone in the room who had received what. By evening, as Pahnke's own dissertation states, every participant had guessed his assignment correctly, although nobody had told them. The double-blind, the pride of the design, held for roughly the first hour.

One of the people in the room was Huston Smith, later one of the best-known scholars of religion in the world; his survey of the world's religions became a standard text in American college classrooms. By his own account he was among those who received the active drug that afternoon. In 1996 he described the experience in an interview with the psychologist Thomas B. Roberts and Robert Jesse of the Council on Spiritual Practices. The peak, Smith said, came with a simple hymn sung by a soprano, "My times are in Thy hand." The melody ends in the most hackneyed way there is, a seventh chord resolving to the tonic. In that setting it became, in his words, the most powerful cosmic homecoming he had ever experienced.

Smith also remembered what no questionnaire recorded: restlessness in the room. Half of those present were in a state where decorum had stopped meaning anything. The other half, the placebo group, were more interested in the spectacle than in the service, with some mocking laughter. A few of them admitted to him the next day that they felt cheated of the experience.

The man on Commonwealth Avenue

Sometime during the afternoon one of the students stands up. He walks unsteadily up the center aisle, climbs into the small pulpit and leafs through the Bible. He mumbles a short, barely intelligible sermon, blesses the congregation with the sign of the cross and walks back, but not to his pew. He heads for the rear exit, down the hallway, and pushes a door that was supposed to be locked. It opens. He is standing on Commonwealth Avenue, in the middle of Boston, in broad daylight.

In Smith's memory it went like this. Before the session, pairs had been formed and each man was supposed to watch his partner. The partner of the student who left did not react. Smith was not responsible, but nobody else got up, so he followed. They had been told the entire basement was sealed off, but something had gone wrong with the instructions to the janitor, and the door at the end of the corridor was open.

On the street the student could not be stopped. Smith saw the wife of a project staff member picnicking on the lawn with her child, called to her to keep an eye on the man, and ran back to the chapel for help. With Pahnke and another helper he caught up with the student just as he entered 745 Commonwealth Avenue, the building of the School of Theology. On the stairs to the third floor they blocked his way. At that moment a mail carrier came up the stairs with an envelope covered in special-delivery stickers. The student snatched it. Finger by finger, Smith said, Pahnke pried the crumpled envelope loose and handed it back to the bewildered mailman.

Back in the chapel, Smith continued, Pahnke injected the man with an antidote. Afterwards he was calm and remembered nothing. Only after twenty-four hours could he put the pieces together: God had chosen him to announce to the world the dawning millennium of peace. In the chapel he had told the small congregation. Outside he had seen the sign reading Dean at the entrance of number 745 and thought that a dean could call a press conference. And the special-delivery letter, he was convinced, was meant for that dean, so he would deliver it.

Here the story becomes an investigation, because there is a second version. Rick Doblin, who interviewed the participants in the 1980s, could not speak to the man himself. He was the only psilocybin participant who refused every conversation, and according to Smith he even threatened to sue if his name was ever published. Doblin therefore summarized what other participants and guides told him secondhand: the student had been deeply moved by the sermon, which stressed that every Christian must tell people about the man who hung on the cross. He may have gone out to do exactly that. After a scuffle, Pahnke injected him with Thorazine, a powerful sedative.

Smith explicitly disagreed on one point. Asked whether anything in Thurman's sermon had pushed the man toward a message, he said not that he had noticed. It was an ordinary Good Friday service, meditations on the seven last words of Jesus. Both sources agree on what matters: a participant lost control, left the building and was given a sedative injection. They differ on the trigger. And the one man who would know has never spoken.

A result that made history

In 1963 Pahnke submitted his dissertation, Drugs and Mysticism. Its conclusion was brief and consequential: the people who received psilocybin experienced, to a greater degree than the controls, the phenomena described by the typology of mysticism. In every category and on every single item, the average of the psilocybin group was higher than that of the controls. Eight of the ten psilocybin participants reported at least seven of the nine features. Pahnke set himself a strict bar, though: an experience only counted as complete at 60 to 70 percent of the maximum score, overall and in every category. Four of the ten psilocybin participants reached it, and none of the controls.

The field was impressed. Walter Houston Clark wrote in 1969 that he knew of no experiment in the history of the scientific study of religion that was better designed or clearer in its results. In 1966 Time picked up the study and made it smoother still: all the students who took the drug had experienced a mystical consciousness resembling that of saints and ascetics.

And the dark side? It is in the dissertation, but quietly. Pahnke mentions that two psilocybin participants had some difficulty reorienting to the ordinary world and had to be calmed by their guides until the effect wore off. In a technical section, and in none of his later publications, he notes that one of the two later called his experience a psychotic episode. Elsewhere he writes that injectable Thorazine was on hand for emergencies. That it was actually used appears nowhere.

Then the window closed. In the spring of 1963 Leary's colleague Richard Alpert was dismissed from Harvard and Leary's contract was not renewed. In 1970 psilocybin was placed in Schedule I, the most restrictive category of the new federal Controlled Substances Act. Pahnke continued for a few years at the Maryland Psychiatric Research Center near Baltimore, studying psychedelic-assisted care for people with terminal cancer. On July 10, 1971, he died in a diving accident in Maine. He would probably have run his own long-term follow-up, Doblin later wrote.

A student goes looking for the participants

In the mid-1980s Rick Doblin was a student interested in exactly this forbidden line of research. In 1986 he founded the nonprofit that became the Multidisciplinary Association for Psychedelic Studies (MAPS), and asked a simple question: what became of the twenty men? A classic test of mystical experience, he wrote, is by its fruits. Someone who believed he had met God twenty-five years ago ought to still say so.

The problem was that all the raw data were lost, including the decoded list of who received which capsule. It took Doblin four years. With the explicit support of Pahnke's widow and the help of most participants, he found nineteen of the twenty. One had died, one could not be located, and two declined: the man from Commonwealth Avenue, out of concern for his privacy, and a control-group participant who still took Pahnke's request for confidentiality literally. Between November 1986 and October 1989 Doblin recorded interviews with sixteen participants, seven from the psilocybin group and nine controls. He visited fifteen of them in their hometowns across the United States. All of them filled out the same questionnaire again that they had completed six months after the experiment.

Mysticism scores, mean across categories, percent of maximum (Doblin 1991, the 16 people re-interviewed)

Group	After 6 months	After 24 to 27 years
Psilocybin (n = 7)	60.8%	66.8%
Placebo, nicotinic acid (n = 9)	11.8%	12.2%

All differences statistically significant according to the author (p < .05). These are self-reports on a questionnaire, not a measurement of the experience itself.

The numbers confirmed Pahnke across a quarter century. All seven psilocybin participants who were interviewed said their experience had genuinely mystical elements and had made a unique contribution to their spiritual lives. None of the controls said so. Some of the changes the men had described after six months concerned career and life decisions; they had lasted, and some had deepened.

But the interviews brought something else to light. Of the seven psilocybin participants, only two had an experience without serious inner struggle. The others described moments when they feared they were going insane, dying, or too weak for what they were going through. One minister, identified by Doblin only by his initials, described how shortly after the capsule he wanted to laugh and then slid into a very strong paranoid experience. The chapel was dark, he hated it, he walked out past a guard. Back inside he saw bars on the windows and felt literally imprisoned. These struggles resolved during the service, and the men now interpret them as part of their growth. But they were there, and in Pahnke's work they barely appear.

"His silence about his administration of a tranquilizer may perhaps have been good politics; certainly it was bad science."
Rick Doblin, The Journal of Transpersonal Psychology 23/1 (1991)

Why the silence?

Doblin's verdict on the Thorazine injection is unambiguous: there is no justification for the omission, however unfairly critics might have used the information. At the same time he tries to understand it. Pahnke presumably feared giving ammunition to opponents of the research. The fear was not imaginary. In 1972 the Oxford scholar of religion R. C. Zaehner claimed in a book that Pahnke had retracted his own findings. Doblin shows that Zaehner had misread a passage about the control group, an example, he writes, of how even among educated scholars bias can overwhelm the facts. Then comes the sentence aimed at both sides: that applies to Pahnke too.

Doblin goes further. Part of the backlash that swept psychedelics out of labs and clinics in the 1960s, he argues, traced back to people who were overwhelmed by frightening experiences outside any research setting, unprepared, and ended up in emergency rooms. Some of those cases, in his view, were connected to the fact that the cautionary side of the Good Friday Experiment had been presented too weakly in the dissertation, in the journals and in the media. The smooth sentence in Time is his example. Downplaying risks and overselling benefits invites the backlash.

That is the real point of the story. The most famous study of psychedelics and religion was not debunked by an opponent but corrected by an advocate. Doblin states explicitly that his data support the main hypothesis and justify further research. He states just as explicitly that the picture of that afternoon that circulated from 1962 to 1991 was incomplete.

Baltimore, 2006: the question returns

For more than thirty years a replication in the United States was practically impossible. Then, in 2006, the psychopharmacologist Roland Griffiths of Johns Hopkins University published a study that the field immediately read as the successor to the Good Friday Experiment. One of the coauthors was William A. Richards, who had published with Pahnke on mysticism and psychedelics in the 1960s. The line from 1962 runs literally into the present.

Griffiths learned from Pahnke's weaknesses. Sessions were individual, not in a group, lasting eight hours, with participants asked to close their eyes and direct their attention inward. The 36 participants, adults who were regularly religiously or spiritually active and had never taken psychedelics, received psilocybin in one session and an active comparison drug, the stimulant methylphenidate, in another. Six more received the comparison drug twice and open-label psilocybin only in a third session, so that nobody could deduce the design from the sequence. People close to the participants were also asked whether they had noticed any changes.

The outcome echoed Boston. Psilocybin raised scores on the mysticism scales, and two months later participants rated the experience as having substantial personal meaning and spiritual significance. One difference from 1962 was right there in the abstract: alongside perceptual changes, psilocybin produced mood changes including anxiety. What Pahnke pushed to the margins now belonged in the first paragraph.

The clergy study: the same question, a new fight

Griffiths' last big question closed the circle back to Good Friday: what happens when not students but experienced religious leaders have this experience? From around 2016, participants at Johns Hopkins and New York University included rabbis, a Catholic priest, several Protestant ministers and a Muslim leader. By lottery, some started right away and others only after a waiting period, serving in the meantime as a comparison group.

Then the study itself made headlines. In March 2024 The New York Times reported on allegations by Matthew Johnson, a longtime colleague of Griffiths and a coauthor. According to Religion News Service, Johnson accused Griffiths of biasing the result by acting as a spiritual leader, framing the trial in spiritual terms and involving funders and legalization advocates in the study itself. A review ordered by the Johns Hopkins ethics board reportedly found indications of serious noncompliance with clinical trial rules. Griffiths could no longer respond; he had died on October 16, 2023.

In February 2025 it looked as if the paper would never appear. Reason quoted, of all people, Rick Doblin, the man who had exposed Pahnke's silence in 1991: it would be a terrible, terrible tragedy if it were not published; it might be the most important paper in the history of psychedelic research. On May 30, 2025, it appeared online in the journal Psychedelic Medicine.

The numbers were more striking than in 1962. Of the 24 clergy who completed both sessions, 96 percent, sixteen months after the second session, counted at least one of the experiences among the five most spiritually significant of their lives, and 92 percent among the five most sacred. Forty-two percent called one of them the single most significant experience of their life. And this time the counterweight was printed right next to it: 46 percent counted a session among the five most psychologically challenging experiences of their lives. According to the study there were no serious adverse events. The authors themselves name the limits: only a wait-list control, a homogeneous sample, some measures not validated.

And where does psilocybin stand in the US today?

Psilocybin remains a Schedule I controlled substance under federal law, the category for drugs with no currently accepted medical use and a high potential for abuse. At the same time the landscape has fractured. Oregon voters approved Measure 109 in 2020, and licensed psilocybin service centers began operating there in 2023. Colorado voters passed Proposition 122 in 2022, which created a regulated natural medicine program. Several cities have made enforcement against personal possession a low priority. None of this changes federal law.

On the medical side, the FDA granted breakthrough therapy designation to psilocybin programs for treatment-resistant depression (2018) and major depressive disorder (2019). That designation speeds up review; it is not an approval. As of this writing, no psilocybin medicine is FDA-approved. None of that is mysticism, but it has a lot to do with Good Friday 1962: it is the same substance whose study began in Boston and stopped in 1970 for decades.

Claim, source, status

Around the Good Friday Experiment circulate sentences that sound more certain than the sources allow. Here are the most common ones, with the source and what holds up today.

Claim	Source	Status
The psilocybin group reported clearly more mystical features.	Pahnke 1963; Doblin 1991	Verified as self-report, at 6 months and at 25 years
The experiment was cleanly double-blind.	Pahnke 1963	Only at the start; by evening everyone knew what they had received
All psilocybin students had a purely positive mystical experience.	Time, 1966	Contradicted: 4 of 10 met Pahnke's threshold; 5 of 7 later interviewees reported serious struggles
A participant was given a sedative injection.	Doblin 1991; Huston Smith 1997	Verified by several witnesses; not mentioned by Pahnke
The sermon drove him into the street.	Doblin 1991, secondhand	Disputed: Smith disagrees, the man himself is silent
Psilocybin makes people lastingly more religious.	Griffiths et al. 2006 and 2025	Not proven: small samples, self-report, partly wait-list only
The experience proves an encounter with God.	Interpretation of individual participants	Not proven: the report is measurable, not its object

Status as of September 2026. "Verified as self-report" means it is documented that people experienced and described it this way, not that the content of their experience corresponds to reality.

The open question

The Good Friday Experiment answers one question and leaves two new ones. Answered: under certain conditions a substance can trigger experiences that people describe in the same words mystics have used for centuries, and that they still count among the most important of their lives a quarter century later. That is well documented, from Boston to Baltimore.

Open, first, is what this experience is. A questionnaire measures what someone reports, not what the report refers to. Whether Huston Smith met something real in that hymn, or whether his brain produced the feeling of such a meeting, no study can decide. Open, second, is how honest research under pressure can be. In 1962 a devout researcher kept quiet about an injection to protect his field. In 2025 colleagues argued over whether another devout researcher loved his field too much. And somewhere a man may still be alive who, on a Good Friday 64 years ago, believed the world had to hear a message. He decided never to talk about it. That belongs to the story too.

If you want to follow the thread further: twenty years after Boston, a psychiatrist in New Mexico was allowed to give volunteers a psychedelic again, this time in a hospital bed, in Rick Strassman's DMT study. What people report when the heart stops, and why both camps cite the same data, is in our piece on near-death experiences and what the studies found. And for the ceremonial side of the same debate, including US law, see ayahuasca: tradition, science and US law. If you are drawn to the experience of stillness without any substance at all, start with our overview of the four families of meditation technique.

Frequently asked questions

What was the Good Friday Experiment?

On Good Friday, April 20, 1962, the physician and minister Walter Pahnke gave 20 Protestant divinity students either psilocybin or nicotinic acid as an active placebo, double-blind, in the basement chapel of Marsh Chapel at Boston University, while they listened to Howard Thurman's Good Friday service. The study was part of his Harvard dissertation. The psilocybin group reported far more features of mystical experience.

What did Walter Pahnke leave out?

One psilocybin participant left the building during the service, was brought back by helpers and was injected with the sedative Thorazine. Pahnke's dissertation only says that Thorazine was available for emergencies, not that it was used. He also treated the serious inner struggles of most psilocybin participants as a side note. Rick Doblin made both public in 1991.

What did Rick Doblin's follow-up find?

Doblin located 19 of the 20 participants and interviewed 16 of them between 1986 and 1989. On the mysticism scales the psilocybin group averaged 66.8 percent of the maximum score and the control group 12.2 percent, almost exactly the six-month values. All seven psilocybin participants interviewed still considered their experience genuinely mystical and valuable. Only two of them had it without serious fear or struggle.

Has the Good Friday Experiment been replicated?

Not literally, but the question has been taken up. Roland Griffiths and colleagues at Johns Hopkins published a double-blind study in 2006 with 36 religiously active adults, comparing psilocybin with the stimulant methylphenidate. A study of clergy from several world religions appeared in 2025 after allegations and an ethics review. Both report great personal meaning, and both report anxiety and difficult moments.

Is psilocybin legal in the US?

Federally, no. Psilocybin is a Schedule I controlled substance. Oregon (since 2023) and Colorado (after a 2022 ballot measure) run state-regulated programs, and some cities deprioritize enforcement, but that does not change federal law. No psilocybin medicine is FDA-approved. This article describes research history and is not encouragement to use it.

Does the experiment prove that God exists?

No. It shows that people on psilocybin in a religious setting report experiences with the same features mystics describe, and that they still consider them meaningful decades later. What gets measured is the report, not what the report refers to. Whether there is a reality behind the experience is something a study like this cannot decide.

Sources and further reading

• Rick Doblin, "Pahnke's 'Good Friday Experiment': A Long-Term Follow-Up and Methodological Critique," The Journal of Transpersonal Psychology 23/1 (1991), pp. 1 to 28 (design, follow-up, scores, Thorazine, the Pahnke, Clark and Time quotes).
• Thomas B. Roberts and Robert N. Jesse, "Recollections of the Good Friday Experiment: An Interview with Huston Smith," The Journal of Transpersonal Psychology 29/2 (1997), pp. 99 to 104 (the hymn, the walk onto Commonwealth Avenue, the mail carrier, the antidote).
• Walter N. Pahnke, Drugs and Mysticism: An Analysis of the Relationship between Psychedelic Drugs and the Mystical Consciousness, PhD dissertation, Harvard University, 1963.
• Walter T. Stace, Mysticism and Philosophy, 1960.
• Roland R. Griffiths, William A. Richards, Una McCann, Robert Jesse, "Psilocybin can occasion mystical-type experiences having substantial and sustained personal meaning and spiritual significance," Psychopharmacology 187 (2006), pp. 268 to 283.
• Roland R. Griffiths et al., "Effects of Psilocybin on Religious and Spiritual Attitudes and Behaviors in Clergy from Various Major World Religions," Psychedelic Medicine (2025).
• Kathryn Post, "After a decade of controversy, clergy psychedelic study is published," Religion News Service, June 2, 2025; Travis Kitchens in Reason, February 9, 2025; Johns Hopkins Medicine press release on Roland Griffiths, October 18, 2023.
• The Harvard Crimson, "In Early 1960's, Experiments With Hallucinogenics Caused Major Uproar, Minor Shake-up," May 27, 2013.
• US law: Controlled Substances Act (21 U.S.C. 812), Schedule I; Oregon Measure 109 (2020); Colorado Proposition 122 (2022).
• Read more on the Desire Diaries: Rick Strassman's DMT study · near-death experiences

This article describes research and history. It is not a guide and not encouragement to use psilocybin, which remains a Schedule I controlled substance under US federal law. If you are struggling, talk to a doctor or therapist; in a crisis, call or text 988. Questions about an order: 28@templeofdesire.com.