Hierarchical structures of affect and psychopathology and their implications for the classification of emotional disorders.

The Diagnostic and Statistical Manual of Mental Disorders-IV groups disorders into diagnostic classes on the basis of the subjective criterion of "shared phenomenological features." The current mood and anxiety disorders reflect the logic of older models emphasizing the existence of discrete emotions and, consequently, are based on a fundamental distinction between depressed mood (central to the mood disorders) and anxious mood (a core feature of the anxiety disorders). This distinction, however, ignores subsequent work that has established the existence of a general negative affect dimension that (a) produces strong correlations between anxious and depressed mood and (b) is largely responsible for the substantial comorbidity between the mood and anxiety disorders. More generally, there are now sufficient data to eliminate the current rational system and replace it with an empirically based taxonomy that reflects the actual-not the assumed-similarities among disorders. The existing structural evidence establishes that the mood and anxiety disorders should be collapsed together into an overarching superclass of emotional disorders, which can be decomposed into three subclasses: the distress disorders (major depression, dysthymic disorder, generalized anxiety disorder, posttraumatic stress disorder), the fear disorders (panic disorder, agoraphobia, social phobia, specific phobia), and the bipolar disorders (bipolar I, bipolar II, cyclothymia). An empirically based system of this type will facilitate differential diagnosis and encourage the ultimate development of an etiologically based taxonomy.