Chapter 26. Anxiety Disorders

Although anxiety has long held a central place in theories of psychopathology, it has only recently been appreciated that the anxiety disorders are the most prevalent category of mental illness in the United States (Kessler et al. 2010) and that they account for approximately a third of the country’s total mental health costs (Lepine 2002). Furthermore, although it has long been recognized that specific neurological lesions may lead to anxiety symptoms (Von Economo 1931), only in recent decades have advances in research allowed specific neuroanatomical hypotheses to be proposed for each of the anxiety disorders. DSM-III (American Psychiatric Association 1980) provided significant impetus to research on anxiety disorders by replacing the category of “anxiety neurosis” with several different conditions and by providing each with operational diagnostic criteria. DSM-IV-TR (American Psychiatric Association 2000) anxiety disorders include panic disorder with and without agoraphobia, social phobia (social anxiety disorder), generalized anxiety disorder (GAD), posttraumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), substance-induced anxiety disorder, and anxiety disorder due to a general medical condition. The DSM-5 (American Psychiatric Association 2013) section on anxiety disorders no longer includes PTSD (which is found in the section on trauma- and stressor-related disorders) or OCD (which is included within the section on obsessive-compulsive and related disorders). For the purposes of this volume, we use the current DSM-5 classification and also retain inclusion of PTSD. In each of the anxiety disorders, it is possible to discern a component comprising anxiety symptoms and a component comprising avoidance symptoms. In GAD, patients have anxiety about the future, and worry may serve as an avoidance behavior. In panic disorder, the anxiety symptoms are those of the panic attack , a discrete period of anxiety that develops rapidly, often spontaneously. The individual also may develop agoraphobia symptoms, or avoidance of those stimuli that appear to promote panic attacks. In social anxiety disorder, panic attacks develop only in the context of performance or other social situations in which the person fears embarrassment or humiliation. As a result of these fears, the person may avoid these situations. In PTSD, in the aftermath of a traumatic event, the person has intrusive experiences, hyperarousal symptoms, negative alterations in cognition and mood, and a range of avoidance and numbing symptoms. In this chapter, we review these developments in our understanding of the anxiety disorders from a neuropsychiatric perspective. The neurochemistry and neuroanatomy of each of the main anxiety disorders and PTSD are considered first. Neurological disorders that may manifest with anxiety symptoms are then discussed, and future directions in the neuropsychiatry of anxiety disorders are considered briefly.