The impact of comorbid anxiety disorders on the course of dysthymic disorder: a 5-year prospective longitudinal study.

BACKGROUND: Few studies have examined the impact of comorbid anxiety disorder on the course of dysthymic disorder despite the high rate of comorbidity between these disorders. This research prospectively examines the naturalistic course of dysthymic disorder in patients with and without a comorbid anxiety disorder over a 5-year period.

METHODS: Thirty-two comorbid patients and 54 non-comorbid patients with dysthymic disorder were assessed at three different time points (baseline, 30 months, and 60 months). Follow-up assessments included the Longitudinal Interval Follow-Up Evaluation and Hamilton Rating Scale for Depression (HRSD).

RESULTS: The rate of recovery from dysthymic disorder was significantly lower in patients with (31.3%) than without (61.1%) comorbid anxiety disorders and, at all three time points, patients with comorbid anxiety had significantly higher HRSD scores. The estimated recovery rate from anxiety disorders was 53.8%. Only five of the comorbid patients recovered from both dysthymic disorder and all anxiety disorders during follow-up. Including new onsets, 72.1% of patients experienced an episode of an anxiety disorder during the 5 years.

LIMITATIONS: There was no pure anxiety disorder group and patients were asked to report on relatively lengthy follow-up intervals.

CONCLUSIONS: While the course of dysthymic disorder is debilitating, these results suggest that the prognosis for patients with a comorbid anxiety disorder is even poorer.