Nonadherence to medical treatment is a major threat to public health and the achievement of therapeutic goals. Poor patient adherence can have serious consequences, including increased disease morbidity and mortality. Patient nonadherence places an appreciable economic burden on the U.S. health care system costing upward of $300 billion annually. Decades of research suggest that improving adherence depends on specific key factors, including: the patient's knowledge and understanding of their disease and treatment regimen, effective interpersonal communication, a collaborative partnership between patient and health professional, a trusting therapeutic relationship, and greater patient satisfaction.