The first seven days of the retreat consisted mainly of breathing exercises and lectures about the karmic cycle of death and rebirth. On the eighth day, the experience turned dark. The instructor told her pupils to imagine that they were decaying corpses and that the bodies of everyone they knew were bags of human shit. The exercise, which is meant to help the students develop psychic tools that they can use in facing their own death, might sound extreme, but Tibetan meditation can get even more far-out: A practice known as Chöd involves meditating over actual decaying corpses in a graveyard.

After the silent retreat ended, the only thing Emily said was, "Maybe more silence would have been better." That night, while the other students chatted enthusiastically in the meditation room, she climbed to the roof, wrapped a khadi scarf around her face, and jumped. A student on his way to bed found her facedown on the pavement. According to the coroner's report, she had died on impact.

I was charged with returning her remains to America. Somewhere along the way, the Indian police gave me her journal. On the eighth day of the retreat, she'd written in flowery, well-constructed cursive, "Contemplating my own death is the key." Then, a few paragraphs later, "I'm scared that I will have this realization and go crazy." One of the last things Emily wrote, in the same steady hand, was "I am a Bodhisattva"—an enlightened being. She believed she was well along the road to transcendence.

Why would a smart, seemingly grounded person like Emily suddenly become so delusional that she would take her own life? Any uncertainty she felt about being in a strange new place may have been compounded by the intensive silent meditation. The principle behind nearly every form of meditation is that by focusing on breathing over an extended period of time, a person can quiet his mind and uncover hidden elements of experience. This is generally regarded as a good thing. These techniques have become so mainstream that most bookstores carry meditation manuals in the self-help section. Many cite the extensive body of research on the benefits of meditation, like MRI scans of Tibetan monks in deep trance states that show how the exercise improves cognition. Dr. Oz and Oprah have both endorsed meditation, and some physicians recommend it as a method of combating hypertension.

Less discussed are the disorienting and damaging side effects of meditation. Neophytes have reported seeing walls move or rooms change color. The introspective state that is one of the goals of meditation can induce feelings of paranoia and terror. According to Willoughby Britton, a neuroscientist at Brown University who studies the effects of meditation on the brain, practitioners can perceive small sounds as cacophonies and lose the sense that they are in control of their own actions. Britton has claimed that this experience, which some refer to as the "dark night," has caused numerous people to wind up on psych wards under suicide watch. Guided visualizations like the one Emily underwent can produce even more profound reactions. These meditation techniques are "designed to completely psychologically rearrange you," says Paul Hackett, a lecturer in classical Tibetan at Columbia University. In a foreign setting, that kind of experience can be even more traumatizing, especially when you take into account the way some Westerners in India tend to snack at the country's spiritual smorgasbord—a little Ashtanga yoga here, some Vipassana meditation there. "People are mixing and matching religious systems like Legos," Hackett says. "It is no surprise that people go insane."

• • •

India syndrome might not even exist if not for the concerted marketing of Eastern religion to the West, and for that we can thank a 19th-century Russian-born mystic named Madame Blavatsky. In 1875, she founded the Theosophical Society in New York City (it later moved to colonial India), using a quasi-scientific methodology to construct a new school of religious thought by packaging ideas and texts from disparate faiths, including Buddhism, Hinduism, Islam, and Zoroastrianism, for enthusiasts in Europe and the United States, making a fortune in the process. A quick inventory of American approaches to Eastern religion—from Emerson and the Transcendentalists to the Beats and the Beatles to David Lynch's Transcendental Meditation foundation—shows the same tendency to bowdlerize enlightenment philosophies to suit Western tastes.

To be sure, many contemporary practitioners of meditation really are seeking inner peace. But some of them may also be looking to unlock something akin to the Jedi powers of Luke Skywalker (many Star Wars aficionados believe Yoda to be based on the Dalai Lama). The Yoga Sutras, a more-than-2,000-year-old text that can be found in almost every yoga studio in the world, devotes an entire chapter to cultivating supernatural abilities. Other books tell not only of yogis' physical feats but also of mental tricks like conversing with the dead and seeing into their students' past lives. Transcendental Meditation promises that, with enough concentration, earnest practitioners can levitate. At Maharishi Mahesh Yogi's Maharishi University of Management in Fairfield, Iowa, followers have spent nearly 40 years practicing "yogic flying," which involves hopping into the air while cross-legged in an effort to become permanently airborne; the maharishi once claimed that thousands were successful.