The Promises and Pitfalls of Psychedelic Use Among Religious Leaders

On 20^th of April, 1962, twenty white male divinity students from Andover Newton Theological School gathered in Boston University’s Marsh Chapel to participate in a scientific experiment. The experiment – commonly known as the ‘Good Friday Experiment’ – was designed by Walter Pahnke, a medical doctor and a graduate student in theology at Harvard Divinity School, as part of his thesis. The participants, who were all psychedelic-naïve, were randomized to receive either psilocybin or nicotinic acid (placebo) and received psychological support prior to and during the experiment. The study aimed to investigate whether administration of psilocybin among religiously inclined individuals, in a highly supportive and religious group setting, would facilitate mystical-type experiences and lasting positive changes in attitudes and behavior.^1,2

The results of the study showed that administration of psilocybin, in this particular setting, was indeed associated with mystical-type experiences and positive changes in attitudes and behavior, relative to administration of placebo.¹ While a follow-up study – involving sixteen of the twenty participants in the original experiment – conducted decades later confirmed these findings,² another experimental study partially replicated the findings from the ‘Good Friday Experiment’ in a sample of thirty-six, psychedelic-naïve participants, all of whom at baseline reported at least sporadic participation in activities of spiritual or religious nature.^3,4 Neither study included fully trained religious professionals, however, who would likely be better suited to compare psilocybin-induced mystical-type experiences with any endogenous mystical-type experiences they might have experienced in the past.

Griffiths and colleagues’ (2025) study builds on these previous scientific experiments and investigates the acute and lasting effects of psilocybin administration in a supportive setting, with psychological support provided throughout the study, among twenty-nine psychedelic-naïve professional religious leaders from four major world religions. The study findings showed that participants randomized to receive psilocybin reported greater positive changes, for example, in their contemplative, prayer or meditation practices, attitudes about their spiritual or religious vocation, and appreciation or understanding of both their own and other religious traditions, compared to participants randomized to the waitlist control group. Notably, sixteen months after the second psilocybin session, ninety-six percent of participants retrospectively rated their psilocybin experience(s) as among the top five most spiritually significant of their lifetime, which should be considered noteworthy for a population that has dedicated a large part of their lives to the spiritual path.⁵

As Griffiths and colleagues’ (2025) note, these findings are promising and could potentially have relevance for supporting religious leaders, including in their religious training and education, in their engagement with contemplative, prayer or meditation practices, or in their interactions with the local community. However, it is important to recognize that psychedelics may not have unidirectional effects on certain outcomes; findings from observational research on belief change and religiosity have indeed been mixed.^6,7 The nature and direction of these types of effects are likely modulated, at least partially, by implicit (or explicit) suggestions from researchers, therapists, or whichever dominant figure might be present during or in close time proximity to the psychedelic experience.⁸ Such considerations are at the center of critiques against Griffiths and colleagues’ (2025) study and highlight the importance of ethical prudence in these contexts.^9,10

While no serious adverse events were reported in Griffiths and colleagues’ (2025) study, it is important to highlight that one participant reported moderate intermittent depressed mood years after their study participation that they attributed to challenging emotional experiences following the second psilocybin session.⁵ It is also important to highlight that one participant in the ‘Good Friday Experiment’ reportedly left the church during the experiment, believing that he had been chosen by God to announce the dawn of the Messianic Age, before receiving a shot of a tranquilizer, Thorazine, to calm down.⁸ Such events – albeit rarely reported in controlled settings – deserve closer scientific attention to ensure safe and ethical practice,¹¹ as well as more balanced reporting in popular media and in industry reports,¹² especially at a time of growing interest in the use of psilocybin and other psychedelics in spiritual or religious settings in, for example, the United States.^13,14

In addition to individual-level risks, psychedelics may also increase the risks of interpersonal harms, which have been sorely understudied to date. Because psychedelics can increase suggestibility,¹⁵ it could potentially render individuals particularly vulnerable to manipulation, coercion, or abuse. For instance, the use of LSD appears to have been part of Charles Manson’s strategy to indoctrinate his cult followers, some of whom were eventually convicted of murders that had been ordered by Manson himself.¹⁶ Such risks may be especially pronounced in spiritual and religious settings, where hierarchical structures and perceived spiritual or religious authority can amplify power imbalances and increase the risks of exploitative dynamics. It is therefore vital to implement safeguards that to the greatest extent possible address both individual and interpersonal risks, including clear ethical guidelines and robust mechanisms for oversight and accountability.

In conclusion, Griffiths and colleagues’ (2025) study on the effects of psilocybin on religious leaders is timely and historically significant. In addition to running a well-designed and impactful experiment, the study authors should be commended for their careful consideration of study limitations and potential risks associated with psychedelics, which should be emulated by other researchers in the field. However, to maximize the potential benefits of psychedelic use among religious leaders and minimize its associated risks, it is crucial that greater scientific and public attention is given to both individual and interpersonal risks, particularly in real-world contexts with potentially heightened risks (e.g., spiritual and religious settings).