Michael, 25, was a certified yoga teacher when he made his way to Cheetah House. He explains that during the course of his meditation practice his “body stopped digesting food. I had no idea what was happening.” For three years he believed he was “permanently ruined” by meditation.

“Recovery,” “permanently ruined”—these are not words one typically encounters when discussing a contemplative practice.

On a cold November night last fall, I drove to Cheetah House. A former student of Britton’s, I joined the group in time for a Shabbat dinner. We blessed the challah, then the wine; recited prayers in English and Hebrew; and began eating.

Britton, an assistant professor of psychiatry and human behavior, works at the Brown University Medical School. She receives regular phone calls, emails, and letters from people around the world in various states of impairment. Most of them worry no one will believe—let alone understand—their stories of meditation-induced affliction. Her investigation of this phenomenon, called “The Dark Night Project,” is an effort to document, analyze, and publicize accounts of the adverse effects of contemplative practices.

The morning after our Shabbat dinner, in Britton’s kitchen, David outlines the history of his own contemplative path. His first retreat was “very non-normal,” he says, “and very good … divine. There was stuff dropping away … [and] electric shocks through my body. [My] core sense of self, a persistent consciousness, the thoughts and stuff, were not me.” He tells me it was the best thing that had ever happened to him, an “orgasm of the soul, felt throughout my internal world.”

David explains that he finally felt awake. But it didn’t last.Still high off his retreat, he declined an offer to attend law school, aggravating his parents. His best friends didn’t understand him, or his “insane” stories of life on retreat.”I had a fear of being thought of as crazy,” he says, “I felt extremely sensitive, vulnerable, and naked.”Not knowing what to do with himself, David moved to Korea to teach English, got bored, dropped out of the program, and moved back in with his parents. Eventually, life lost its meaning. Colors began to fade. Spiritually dry, David didn’t care about anything anymore. Everything he had found pleasurable before the retreat—hanging out with friends, playing music, drinking—all of that “turned to dirt,” he says, “a plate of beautiful food turned to dirt.”He traveled back and forth from Asia to home seeking guidance, but found only a deep, persistent dissatisfaction in himself. After “bumming around Thailand for a bit,” he moved to San Francisco, got a job, and sat through several more two- and 10-week meditation retreats. Then, in 2012, David sold his car to pay for a retreat at the Cloud Mountain Center that torments him still.

“Psychological hell,” is how he describes it. “It would come and go in waves. I’d be in the middle of practice and what would come to mind was everything I didn’t want to think about, every feeling I didn’t want to feel.” David felt “pebble-sized” spasms emerge from inside a “dense knot” in his belly.

He panicked. Increasingly vivid pornographic fantasies and repressed memories from his childhood began to surface.“I just started freaking out,” he says, “and at some point, I just surrendered to the onslaught of unwanted sexual thoughts … a sexual Rolodex of every taboo.” As soon as he did, however, “there was some goodness to it.” After years of pushing away his emotional, instinctual drives, something inside David was “reattached,” he says.Toward the end of his time at the Cloud Mountain Center, David shared his ongoing experiences with the retreat leaders, who assured him it was probably just his “ego’s defenses” acting up. “They were really comforting,” he says, “even though I thought I was going to become schizophrenic.”

According to a survey by the National Institutes of Health, 10 percent of respondents—representing more than 20 million adult Americans—tried meditating between 2006 and 2007, a 1.8 percent increase from a similar survey in 2002. At that rate, by 2017, there may be more than 27 million American adults with a recent meditation experience.

In late January this year, Time magazine featured a cover story on “the mindful revolution,” an account of the extent to which mindfulness meditation has diffused into the largest sectors of modern society. Used by “Silicon Valley entrepreneurs, Fortune 500 titans, Pentagon chiefs, and more,” mindfulness meditation is promoted as a means to help Americans work mindfully, eat mindfully, parent mindfully, teach mindfully, take standardized tests mindfully, spend money mindfully, and go to war mindfully. What the cover story did not address are what might be called the revolution’s “dirty laundry.”

“We’re not being thorough or honest in our study of contemplative practice,” says Britton, a critique she extends to the entire field of researchers studying meditation, including herself.I’m sitting on a pillow in Britton’s meditation room. She tells me that the National Center for Complementary and Alternative Medicine’s website includes an interesting choice of words in its entry on meditation. Under “side effects and risks,” it reads:“Meditation is considered to be safe for healthy people. There have been rare reports that meditation could cause or worsen symptoms in people who have certain psychiatric problems, but this question has not been fully researched.”By modern scientific standards, the aforementioned research may not yet be comprehensive—a fact Britton wants to change—but according to Britton and her colleagues, descriptions of meditation’s adverse effects have been collecting dust on bookshelves for centuries.The phrase “dark night of the soul,” can be traced back to a 16th-century Spanish poem by the Roman Catholic mystic San Juan de la Cruz, or Saint John of the Cross. It is most commonly used within certain Christian traditions to refer to an individual’s spiritual crisis in the course of their union with God.

The divine experiences reported by Saint John describe a method, or protocol, “followed by the soul in its journey upon the spiritual road to the attainment of the perfect union of love with God, to the extent that it is possible in this life.” The poem, however, is linked to a much longer text, also written by Saint John, which describes the hardships faced by those who seek to purify the senses—and the spirit—in their quest for mystical love.

According to Britton, the texts of many major contemplative traditions offer similar maps of spiritual development. One of her team’s preliminary tasks—a sort of archeological literature review—was to pore through the written canons of Theravadin, Tibetan, and Zen Buddhism, as well as texts within Christianity, Judaism, and Sufism. “Not every text makes clear reference to a period of difficulty on the contemplative path,” Britton says, “but many did.”“There is a sutta,” a canonical discourse attributed to the Buddha or one of his close disciples, “where monks go crazy and commit suicide after doing contemplation on death,” says Chris Kaplan, a visiting scholar at the Mind & Life Institute who also works with Britton on the Dark Night Project.Nathan Fisher, the study’s manager, condenses a famous parable by the founder of the Jewish Hasidic movement. Says Fisher, “[the story] is about how the oscillations of spiritual life parallel the experience of learning to walk, very similar to the metaphor Saint John of the Cross uses in terms of a mother weaning a child … first you are held up by a parent and it is exhilarating and wonderful, and then they take their hands away and it is terrifying and the child feels abandoned.”Kaplan and Fisher dislike the term “dark night” because, in their view, it can imply that difficult contemplative experiences are “one and the same thing” across different religions and contemplative traditions.

Fisher also emphasizes two categories that may cause dark nights to surface. The first results from “incorrect or misguided practice that could be avoided,” while the second includes “those [experiences] which were necessary and expected stages of practices.” In other words, while meditators can better avoid difficult experiences under the guidance of seasoned teachers, there are cases where such experiences are useful signs of progress in contemplative development. Distinguishing between the two, however, remains a challenge.Britton shows me a 2010 paper written by University of Colorado-Boulder psychologist Sona Dimidjian that was published in American Psychologist, the official journal of the American Psychological Association. The study examines some dramatic instances where psychotherapy has caused serious harm to a patient. It also highlights the value of creating standards for defining and identifying when and how harm can occur at different points in the psychotherapeutic process.One of the central questions of Dimidjian’s article is this: After 100 years of research into psychotherapy, it’s obvious that scientists and clinicians have learned a lot about the benefits of therapy, but what do we know about the harms? According to Britton, a parallel process is happening in the field of meditation research.”We have a lot of positive data [on meditation],” she says, “but no one has been asking if there are any potential difficulties or adverse effects, and whether there are some practices that may be better or worse-suited [for] some people over others. Ironically,” Britton adds, “the main delivery system for Buddhist meditation in America is actually medicine and science, not Buddhism.”

As a result, many people think of meditation only from the perspective of reducing stress and enhancing executive skills such as emotion regulation, attention, and so on.For Britton, this widespread assumption—that meditation exists only for stress reduction and labor productivity, “because that’s what Americans value”—narrows the scope of the scientific lens. When the time comes to develop hypotheses around the effects of meditation, the only acceptable—and fundable—research questions are the ones that promise to deliver the answers we want to hear.”Does it promote good relationships? Does it reduce cortisol? Does it help me work harder?” asks Britton, referencing these more lucrative questions. Because studies have shown that meditation does satisfy such interests, the results, she says, are vigorously reported to the public. “But,” she cautions, “what about when meditation plays a role in creating an experience that then leads to a breakup, a psychotic break, or an inability to focus at work?”Given the juggernaut—economic and otherwise—behind the mindfulness movement, there is a lot at stake in exploring a shadow side of meditation. Upton Sinclair once observed how difficult it is to get a man to understand something when his salary depends on his not understanding it. Britton has experienced that difficulty herself. In part because university administrators and research funders prefer simple and less controversial titles, she has chosen to rename the Dark Night Project the “Varieties of Contemplative Experience.”

Britton also questions what might be considered the mindfulness movement’s limited scope. She explains that the Theravadin Buddhist tradition influences how a large portion of Americans practice meditation, but in it, mindfulness is “about vipassana, a specific type of insight … into the three characteristics of experience.” These are also known as the three marks of existence: anicca, or impermanence; dukkha, or dissatisfaction; and anatta, or no-self.

In this context, mindfulness is not about being able to stare comfortably at your computer for hours on end, or get “in the zone” to climb the corporate ladder. Rather, says Britton, it’s about the often painstaking process of “realizing and processing those three specific insights.”

Shinzen Young, a Buddhist meditation teacher popular with young scientists, has summarized his familiarity with dark night experiences. In a 2011 email exchange between himself and a student, which he then posted on his blog, Young presents an explanation of what he means by a “dark night” within the context of Buddhist experience:

“Almost everyone who gets anywhere with meditation will pass through periods of negative emotion, confusion, [and] disorientation. …The same can happen in psychotherapy and other growth modalities. I would not refer to these types of experiences as ‘dark night.’ I would reserve the term for a somewhat rarer phenomenon. Within the Buddhist tradition, [this] is sometimes referred to as ‘falling into the Pit of the Void.’ It entails an authentic and irreversible insight into Emptiness and No Self. Instead of being empowering and fulfilling … it turns into the opposite. In a sense, it’s Enlightenment’s Evil Twin. This is serious but still manageable through intensive … guidance under a competent teacher. In some cases, it takes months or even years to fully metabolize, but in my experience the results are almost always highly positive.”

Britton’s findings corroborate many of Young’s claims. Among the nearly 40 dark night subjects her team has formally interviewed over the past few years, she says most were “fairly out of commission, fairly impaired for between six months [and] more than 20 years.”