Clinical Obsessive-Compulsive Disorder (OCD) is distinguished from "normal" obsessions and compulsions primarily by the frequency and intensity of the symptoms, and the extent to which they interfere with daily functioning. In this book, the authors present current research in the study of the symptoms, prevalence and psychological treatments for OCD. Topics discussed include the role of Comorbid Personality Disorders (CPDs) in Obsessive-Compulsive Disorder (OCD); the adaptive significance of and natural expression of obsessive and compulsive-like symptoms; OCD in children; cognitive techniques for OCD treatment; the dimensionality of OCD symptoms; internet-based cognitive behaviour therapy for OCD; the phenomenology, correlates and psychosocial impact of obsessive-compulsive love; the importance of quality of life in patients with OCD; and an investigation into the dimensions of OCD symptoms in patients with Tourette Syndrome.