Generalized anxiety disorder and its comorbidities: disputes at the boundaries.

This theoretical paper reviews the status of generalized anxiety disorder (GAD) and the Axis I and Axis II disorders with which it is often comorbid. Differences in comorbidity between the epidemiological and clinical literatures are discussed. Special attention is given to panic disorder, the symptoms of which are similar to those of GAD. The boundaries of GAD and its relationship to other Axis I disorders and to Axis II disorders raise important implications for its classification.