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On April 20, 1962, a group of theology students and professors gathered outside Boston University’s Marsh Chapel, waiting for Good Friday services to begin. These particular services were to be unlike any other: On their way into the chapel, Harvard psychiatrist Walter Pahnke administered the group a dose of psychedelic mushrooms.

As part of his Ph.D. thesis under Timothy Leary and Richard Alpert (aka Ram Dass), Pahnke sought to test his hypothesis that psychedelic drugs, taken in a religious setting, could provoke a genuine spiritual experience. His investigation would go down in psychedelic history as the “Good Friday experiment.”

He was right. Nine out of the 10 students who took the mushrooms reported having a mystical experience. One of those students was the historian Huston Smith, who went on to write Cleansing the Doors of Perception, a classic philosophical work exploring the potential of psychedelic drugs as entheogens, or “God-revealing chemicals.”

“The experience was powerful for me, and it left a permanent mark on my experienced worldview,” Smith, who passed away in December, reflected. “I had believed in God... but until the Good Friday experiment, I had no personal encounter with God of the sort that bhakti yogis, Pentecostals and born-again Christians describe.”

Today, another research project is taking up where the Good Friday experiment left off ― this time, with modern research tools and leaders from not just the Christian faith but an array of world religions.

As part of a small pilot study, psychologists at Johns Hopkins and New York University are giving psilocybin, the active ingredient in magic mushrooms, to spiritual leaders. Their aim is to demystify the transcendent and deeply meaningful experiences that people often report having under the influence of psychedelic drugs.

A Zen Buddhist roshi and an Orthodox Jewish rabbi have embarked on consciousness-expanding journeys in the name of science, along with Episcopal, Presbyterian and Eastern Orthodox Christian clergy. The research team is about halfway done with the study, which will include a total of 24 participants. (They’re still looking for Muslim imams and Catholic and Hindu priests.)

“They’re helping us map out this landscape of mystical experience with their incredible training and experience,” Dr. Anthony Bossis, project director of the NYU Psilocybin Religious Leaders Project, told The Huffington Post.

By working with leaders of different faiths, the researchers hope to learn something about the shared mystical core of all the world’s major religions ― what the author Aldous Huxley called the “perennial philosophy.” Understanding these mystical experiences might also shed light on the therapeutic benefits of psilocybin and other psychedelic drugs, which researchers are exploring as treatment options for post-traumatic stress disorder, end-of-life anxiety and depression, addiction and other psychological conditions.

“If you give psilocybin psychedelics to 20 different people, you get 20 different experiences,” Bossis said. “But there is a common mystical experience... It seems that the efficacy of these medicines is in their ability, pretty reliably in the right set and setting, to activate or trigger this mystical experience.”

This experience of deep connection with the sacred can have long-lasting effects. Mushroom-triggered mystical experiences have been linked with positive changes in behavior and values, and with lasting increases in the personality domain of openness to experience, which encompasses intellectual curiosity, imagination, adventure-seeking and engagement with music and art. People commonly report that the experience is one of the most personally and spiritually meaningful of their lives.

“"They’re helping us map out this landscape of mystical experience with their incredible training and experience."” - Dr. Anthony Bossis, clinical assistant professor, NYU School of Medicine

Finding Words for the Indescribable

The term “mystical experience” might not sound especially rigorous, but it’s something that has actually been studied in depth. Psychologists define the experience based on its major components, including a sense of sacredness, feelings of unity, ineffability, peace and joy, transcendence of time and space and feelings of being confronted with some objective truth about reality.

The experiences are often said to be impossible to put into words. But Bossis and his colleagues hope that the unique expertise of these spiritual leaders will provide greater insight into their workings.

“One of things I was struck by, doing this research, was the experience of love that they spoke of,” he said. “It’s quite striking to witness... people speak about this overwhelming experience of love ― loving-kindness to self, love towards others, and what the Greeks called agape, this kind of universal, cosmic love that they say permeates everything, and which recalibrates how they live.”

You may feel tempted to brush off this sort of talk as mere drug-induced reverie. (One thinks of the Onion article “Universe Feels Zero Connection To Guy Tripping On Mushrooms.”) But early research and anecdotal reports suggest that chemically induced mystical experiences may not be so different from those that occur as a result of years of meditation and prayer.

Mystical experiences, whether drug-induced or spontaneously occurring, seem to connect the individual with the mystical core of all the world’s major religions ― a sense of unity, oneness and interconnection with all beings.

“I think to understand the depth of religion, one needs to have firsthand experience,” said Jewish Renewal movement leader Rabbi Zalman Schacter Shalomi in an interview published in 2005. “It can be done with meditation. It can be done with sensory deprivation. It can be done a number of ways. But I think the psychedelic path is sometimes the easiest way, and it doesn’t require the long time that other approaches usually require.”

The Psychedelic Renaissance

The psychedelic path has led many people, including the American Buddhist teacher Jack Kornfield, to take up more traditional spiritual practices as a way to stay connected in their daily lives to the sorts of insights and sensations they first experienced with psychedelics.

“In spiritual communities, we need an honest exploration of this delicate and sometimes taboo topic,” Kornfield wrote in 2015. “Let us approach the use of these drugs consciously.”

While psychedelics may have a stigma attached in today’s culture, altered states of consciousness have long been an aspect of human spirituality, and they’ve featured in religious rituals around the world for thousands of years.

For the past several years, entheogens have been quietly making their way into modern medicine. A landmark study from NYU and Hopkins, published last month in the Journal of Psychopharmacology, showed a single dose of psilocybin to be effective in relieving death-related anxiety in cancer patients.

““A return to entheogens for the treatment of psycho-existential suffering may signal that medicine has come full circle to embrace the earliest known approach to healing our deepest of human agonies."” - Dr. Craig Blinderman, director of adult palliative care services at Columbia University Medical Center/New York-Presbyterian Hospital

In a majority of the patients, the psilocybin triggered a mystical experience, which may be largely responsible for the renewed sense of meaning and relief from existential distress described by the patients. In fact, the extent to which the patients experienced reductions in depression, anxiety and fear of death correlated directly with the intensity of the mystical experience.

“Increasingly, it appears that the mystical-type experiences measured immediately after a session is predictive of enduring positive effects,” Dr. Roland Griffiths, a psychologist at Johns Hopkins and one of the study’s lead authors, told HuffPost. “That’s consistent across studies of healthy volunteers, addicted cigarette smokers, and in psychologically distressed cancer patients. There’s something about the nature of those experiences that is predictive of subsequent positive effects.”

Dr. Craig Blinderman, director of adult palliative care services at Columbia University Medical Center/New York-Presbyterian Hospital, said the research presents an exciting meeting of the minds between modern medicine and ancient healing modalities.