In the late 1960s, Czech psychotherapist Stanislav Grof concluded, through his research on LSD at John Hopkins University, that psychedelic drugs could help treat emotional trauma—but without easy access to them, patients couldn’t take advantage of his findings. As an alternative, he and his late wife, the author and a psychotherapist Christina Grof, developed holotropic breathwork, a series of breathing techniques meant to induce “natural” psychedelic states through controlled hyperventilation that could be achieved without taking the illicit substance.