Generalized anxiety disorder (GAD) is characterized by chronic and persistent worry. These worries are multigenic (e.g., about finances, family, health, and the future), excessive, and difficult to control, and are often accompanied by other nonspecific psychological and somatic symptoms (Table 1). The term “generalized anxiety disorder” may incorrectly imply that anxiety symptoms are entirely nonspecific, and this misconception may sometimes lead to inappropriate use of this diagnosis by almost all anxious patients. A new term, generalized worry disorder, could be used, although it is not used in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). In fact, however, the core and defining characteristic of GAD is excessive worry. Epidemiological surveys show that the past-year prevalence of GAD is 3.1% and the lifetime prevalence is 5.7% in the U.S. population as a whole; the prevalence is approximately twice as high in women as in men, and the age of onset of GAD is highly variable: some individuals develop it in childhood, most begin in early adulthood, and another peak occurs in old age, often in the context of chronic physical illness. By definition, GAD is a chronic disorder, with 6 months being the minimum length of time to diagnose anxiety, and most patients have been suffering from the disorder for several years before seeking treatment. GAD is particularly prevalent in primary care settings, being present in 7-8% of patients. However, patients rarely report symptoms of worry. Children with GAD often present with recurrent abdominal pain and other physical symptoms that may keep them away from school. Depression is a common co-morbidity of GAD, although depression may be difficult to distinguish from GAD because many GAD symptoms (such as fatigue and insomnia) overlap with depressive symptoms. Persistent lack of pleasure (inability to experience pleasure) is a core symptom of depression, but not of anxiety. individuals with GAD often describe a sense of helplessness, whereas individuals with depression may often feel hopeless. However, individuals with GAD are at higher risk for intentional self-injury, including suicide attempts. For many patients, GAD is a state of potential ups and downs – bouts of depression in the midst of particular life stressful situations. This combination of dual GAD and depression is sometimes referred to as “anxious depression” and is particularly common in primary care settings. Functional neuroimaging studies of GAD patients show increased activation of the limbic system (e.g., amygdala) and decreased activation of the prefrontal cortex; other evidence suggests that functional connectivity between these regions is diminished. In addition, preliminary data suggest that effective treatments for the disease may repair the abnormal brain function described above. For example, functional magnetic resonance imaging (fMRI) shows that patients with GAD have elevated levels of amygdala activation, while CBT attenuates their activation status.