Anxiety is a widespread and universal problem with significant adverse effects on mental health and quality of life. This book examines the phenomenology, psychopathology, and biological mechanisms of anxiety disorders. Over three sections, the book examines various social and clinical aspects of anxiety as well as neurobiological data and pathogenesis of anxiety disorders such as Capgras syndrome and de Clerambault’s syndrome. It also presents results of immunological and neurochemical studies of some anxiety states.