The Science of Yoga

neuroscience research as well as its extensive roster of celebrity patients, including the mathematician John Nash, the poet Sylvia Plath, and the musician James Taylor.
    Chris C. Streeter, the head of the team, held faculty appointments in psychiatry and neurology at the Boston University School of Medicine and lectured in psychiatry at the Harvard Medical School. Plus, she knew yoga and knew people who knew yoga. Her team focused on an important chemical in the human brain that goes by the tongue-twisting name of gamma-aminobutyric acid—or, easier to say, GABA. It is a major neurotransmitter and regulator of the human nervous system. Many reports have linked depression to low GABA levels. So a smart question was whether yoga went about easing depression by raising concentrations of the neurotransmitter.
    Scientists have known about GABA since the 1950s. But it took a long time to understand its role in the brain and to develop the scientific tools to easily track its comings and goings. GABA works by blocking actions rather than causing them. It is known as an antagonist. Such chemicals, when they bind to cellular receptor sites in the nervous system, disrupt interactions and inhibit the functions of other neurotransmitters. In general, GABA slows the firing of neurons, making them less excitable. So high levels of the neurotransmitter have a calming effect. When alcohol and drugs like Valium bind to GABA receptor sites, they increase the molecule’s efficiency and thus promote its actions as a sedative and a muscle relaxant. GABA itself tends to promote relaxation and reduce anxiety.
    By the 2000s, brain imaging had advanced to the point that tracking GABA could be done fairly inexpensively. Scientists judged the time right to address the yoga question.
    The team found lots of potential subjects. Boston, starting with Thoreau and James, had evolved into a yoga hotspot. In modern times, it pulsed with many thousands of practitioners.
    The team selected eight who practiced a number of diverse styles. They were Ashtanga (the gymnastic style developed by Pattabhi Jois, a student of Krishnamacharya’s), Bikram (the hot yoga of Choudhury), Hatha (the ancient classic), Iyengar (the modern classic), Kripalu (developed by the Berkshires center), Kundalini (the heavy-breathing style popularized by Yogi Bhajan, a Sikh mystic), Power (an aggressive form of Ashtanga), and Vinyasa (a flowing style developed relatively late in life by Krishnamacharya and popularized by his student Srivatsa Ramaswami). The subjects had practiced yoga anywhere from two to ten years. They were all white, mostly female, mostly single, and averaged twenty-six years in age. Prior to the study, all had practiced yoga at least twice a week.
    The team measured GABA levels before and after an hour-long yoga session. The routine was standardized to focus on asanas and related breathing. At the startand end, the students could engage in brief sessions of quiet contemplation. But they were allowed no extensive periods of meditation or pranayama. The study guidelines called for at least fifty-five minutes of common asanas, such as inversions and backbends, twists and Sun Salutations. To ensure a degree of standardization, a research staff member with yoga training observed the sessions. The scientists compared the eight yoga practitioners to a control group of eleven individuals who did no yoga but instead read magazines and popular fiction for an hour.
    The results, published in 2007, fairly glowed. The scientists found that the brains of yoga practitioners showed an average GABA rise of 27 percent. By contrast, the comparison group experienced no change whatsoever. Moreover, the yoga practitioners with the most experience or who practiced the most during the week tended to have real GABA surges. For instance, the practitioner who had done yoga for a decade experienced a GABA rise of 47 percent. One participant who practiced yoga five times a week had an increase of 80 percent, the levels of the neurotransmitter almost doubling.
    The scientists concluded that yoga showed much promise for treating anxiety and depression. Perry F. Renshaw, a senior author of the study and director of brain imaging at the McLean Hospital, noted with understatement that any proven therapy that is cheap, widely available, and shows no side effects has “clear public health advantages.”
    Encouraged, the team embarked on a new study. This time the scientists looked at