Self-determination theory is grounded in the belief that people work best and are happiest when they feel that they are in control of their own lives. This text explains the ramifications of the theory and provides clinical examples to show that it can be used to motivate patients undergoing treatment for such physical or psychological issues as diabetes management, smoking cessation, post-traumatic stress, obsessive-compulsive disorder and depression. The first part of the text provides historical background to self-determination theory, showing that it is humanistically oriented and has three decades of empirical research behind it. In the process, the authors discuss why humanistic psychology fell out of favour in academic psychology; why "self-help" and New Age books have such perennial popularity; and why it is so important for authorities to support patients' sense of self. The remainder of the volume presents many specific case examples to describe the theory's application.