Johns Hopkins University’s 2006 psilocybin study marked a turning point in the book’s account of modern psychedelic research: it suggested that researchers could deliberately occasion experiences people regarded as profoundly meaningful, then investigate their lasting effects using scientific methods. The study did not resolve what such experiences mean or where their apparent insights come from. Instead, it made those questions newly available to systematic inquiry.

Researching Mystical Experience

Roland Griffiths’s encounters with volunteers in the 2006 study renewed his commitment to science while deepening his respect for what remained unknown. He described the experiences as unprecedented in their depth of meaning and lasting spiritual significance. In his view, what distinguished psychedelics from other drug experiences was not simply what participants felt during a session, but the meaning they carried away from it.

The study also offered Griffiths a way to approach mystical states prospectively. If researchers could create conditions under which a substantial proportion of participants reported one of the most meaningful experiences of their lives, they could study such states as they occurred rather than relying only on retrospective accounts. Griffiths cited a figure of 70 percent in describing the probability with which this kind of experience could be occasioned. For him, this gave scientific research a new point of entry into a field that had often been treated as private, ineffable, or beyond measurement.

Follow-Up and Lasting Change

A follow-up study examined the first groups of healthy volunteers studied at Johns Hopkins. Psychologist Katherine MacLean analyzed survey data from 52 participants, alongside follow-up interviews with friends and family members whom the volunteers had designated. The results connected the lasting effects of the experience with the character of the experience itself: participants whose scores indicated a complete mystical experience showed lasting improvements in well-being and long-term increases in openness to experience.

Openness is one of five broad personality traits used by psychologists, alongside conscientiousness, extroversion, agreeableness, and neuroticism. It encompasses aesthetic sensitivity, imagination, and tolerance of other people’s viewpoints and values; it is also associated with creativity in the arts and sciences. The reported changes were notable in part because pronounced, lasting shifts in adult personality are uncommon. The findings therefore extended the study’s significance beyond an account of what participants experienced during a session: they raised the possibility that a deliberately occasioned experience could be associated with durable changes in how people approached life and ideas.

Meaning and the Limits of Interpretation

The study’s findings did not settle whether the experiences’ apparent spiritual content referred to anything beyond the mind. Griffiths remained agnostic about volunteers’ reports of encountering a reality beyond ordinary experience. He was willing to hold open the possibility that those reports might or might not be true, while treating their investigation as a scientific opportunity. The distinction mattered: the reported meaning could be studied without the researchers having to declare its ultimate source.

That restraint sits alongside an older history of interpreting mushroom experiences through religious frameworks. Indigenous sacramental practices had been driven underground after the Spanish conquest, and sixteenth-century accounts describe varied responses to mushrooms, including visions, singing, dancing, weeping, and later discussion of what participants had seen. By the time R. Gordon Wasson attended a Mazatec ceremony in 1955, many Mazatecs were Catholic and used mushrooms for healing and divination, including seeking lost people or objects. Wasson, however, brought a theory about the origins of religion and framed the ceremony as a form of holy communion. The contrast warns against treating very different practices and accounts as interchangeable simply because they involve powerful experiences. The Hopkins study could investigate reported mystical effects; it could not, by its findings alone, establish a single religious meaning for them.

Scientific and Therapeutic Consequences

For Griffiths, the study opened a new frontier for scientific exploration. Its importance was methodological as well as personal: researchers could prospectively occasion mystical states with a high degree of probability and then examine their effects. He described the prospect with the enthusiasm of someone newly returned to a field of discovery, while acknowledging that the central mystery remained open.

The research also helped sustain wider institutional work at Johns Hopkins. By 2015, around twenty people there were working on studies involving psychedelics, a level of institutional support the book compares with the earlier work at Spring Grove. The lab continued to investigate spirituality and the betterment of healthy people, including trials involving long-term meditators and religious professionals. At the same time, the possibility that mystical experience might have therapeutic value led researchers to study applications including addiction and the existential distress associated with terminal illness. These later lines of investigation were not identical to the original study, but they followed from its central proposition: that a carefully studied psychedelic experience could have consequences extending well beyond the session itself.