Introduction

Abstract Obsessive-compulsive disorder and related disorders (OCRDs) constitute some of the most important conditions in psychiatry. Obsessive-compulsive disorder (OCD) is one of the most prevalent and disabling of the psychiatric disorders and comprises a paradigmatic exemplar of a neuropsychiatric disorder, providing translational research with a unique opportunity to develop an integrated cognitive-affective neuroscience approach to psychiatric disorder. In the recent revision of Diagnostic and Statistical Manual of Mental Disorders (DSM-5), OCD is now grouped within a new chapter on obsessive-compulsive and related disorders, together with body dysmorphic disorder, hoarding disorder, trichotillomania (hair-pulling disorder), and excoriation (skin-picking) disorder. There is a growing database of randomized controlled trials of treatment of OCD and OCRDs, allowing for an evidence-based approach to their management. This volume will summarize the phenomenology, pathogenesis, pharmacotherapy, and psychotherapy of OCD and related disorders.