Infrequency of "pure" GAD: impact of psychiatric comorbidity on clinical course.

The widespread occurrence of psychiatric comorbidity among patients with generalized anxiety disorder (GAD) has been well documented. However, there is a paucity of studies examining the impact comorbid disorders have on the clinical course of GAD. In this study, 179 patients with GAD at intake, 12 patients with a past history of GAD, and 109 patients who subsequently onset a first episode of GAD during the course of follow-up were followed for 8 years in this naturalistic, prospective study of anxiety disorders. Results indicate that comorbid anxiety, mood, and substance use disorders are very common with GAD and increased during follow-up. For example, 39% of participants with GAD also had a comorbid diagnosis of major depressive disorder at intake and increased to 65% at 4 years and 74% at the 8-year follow-up. Inspection of "pure" cases of GAD indicated that out of 20 patients with GAD alone at intake, all but 1 went on to develop some comorbidity. Results also indicate that being in episode of comorbid MDD or panic disorder with agoraphobia decreased the probability that a subject would remit from their GAD. The findings highlight the need for such long-term, prospective research since results show that patients with GAD at intake had increasing risk for developing other mental disorders during subsequent follow-ups. Additionally, results of such high comorbidity and the impact of these comorbid disorders on the clinical course of GAD should have a notable impact on research into the treatment of GAD.