Introduction/Depression and Anxiety: Implications for Nosology, Course, and Treatment

International epidemiologic and clinical studies have shown that comorbid depression and anxietyis of major importance, resulting in more severe symptoms, impairment, subjective distress, and longitudinalcourse than either anxiety or depression alone. Threshold and subthreshold levels of anxiety("A," "a") and depression ("D," "d") can be defined on the basis of duration, frequency, impairment,and number of symptoms. These letters can then be used to designate the various combinations ofdepression and anxiety, e.g., AD, aD. Current evidence demonstrates the importance of evaluatingboth threshold and subthreshold levels of depression and anxiety.