DEPRESSION AND ANXIETY - IMPLICATIONS FOR NOSOLOGY, COURSE, AND TREATMENT - INTRODUCTION

International epidemiologic and clinical studies have shown that comor bid depression and anxiety is of major importance, resulting in more s evere symptoms, impairment, subjective distress, and longitudinal cour se 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 o f symptoms. These letters can then be used to designate the various co mbinations of depression and anxiety, e.g., AD, aD. Current evidence d emonstrates the importance of evaluating both threshold and subthresho ld levels of depression and anxiety.