Part 4, Obsessive-Compulsive Disorder and Related Disorders, part 5, Panic Disorders and Agoraphobia, part 6, Social Phobias, and part 8, Posttraumatic Stress Disorder and Acute Stress Disorders, each contains four chapters—on phenomenology, pathogenesis, pharmacotherapy, and psychotherapy of the particular disorder. Part 7, Specific Phobia, reverts to a single-chapter format. Part 9, Anxiety Disorders in Special Populations, contains four chapters. These deal with anxiety in children and adolescents, in the elderly, in the context of substance abuse, and in medical settings. Part 10, Social Aspects of Anxiety Disorders, has three chapters: "Cultural and Social Aspects of Anxiety Disorders," "Economic Costs of Anxiety Disorders," and "Consumer Considerations."