The history, philosophy, ethics, and science behind the placebo and nocebo effects. Placebos are the most widely used treatments in the history of medicine. Thousands of studies show that they can be effective and make us happier and healthier. Yet confusion about what placebos are and how to measure their effects prevents some doctors from using them to help patients. Meanwhile, damage caused by the nocebo effect—the negative effect of expecting something bad—is not widely recognized. In The Power of Placebos, Jeremy Howick provides an interdisciplinary perspective on placebos and nocebos based on more than twenty years of research and data from over 300,000 patients. This book, the culmination of that research, offers practical ways for researchers, policymakers, and doctors to put placebo and nocebo research into practice to improve health outcomes. In addition to providing an overview of placebos and nocebos and explaining how belief systems and context can create physiological effects in the body, Howick advocates for a number of controversial positions, including why it may be unethical to include placebos in most clinical trials in which there are already established therapies and why physicians should consider using placebos regularly in their practices. Howick also underscores the importance of the therapeutic effects of interactions between health care practitioners and patients, in the context of care. The Power of Placebos dispels the confusion surrounding placebos and paves the way for doctors to help patients by enhancing placebo effects and avoiding the pitfalls of nocebos.