The course of depressive symptoms in older adults with comorbid major depression and dysthymia.

OBJECTIVE: To examine the course of depressive symptoms in older patients with comorbid major depression and dysthymia.
DESIGN: Secondary data analysis using both proportional hazards modeling and a repeated measures mixed model.
SETTING: Clinical Research Center for the Study of Depression in Later Life conducted at Duke University. PARTICIPANTS: Two hundred fifty inpatients and outpatients age 60 and older with major depression enrolled in a naturalistic treatment study and followed up for 10 years. MEASUREMENTS: The Diagnostic Interview Schedule was used to confirm a clinical diagnosis of major depression and to identify patients with comorbid dysthymia at the time of study enrollment. Patients were administered the Montgomery-Asberg Depression Rating Scale (MADRS) every 3 months. For the proportional hazards models, partial remission was defined as a MADRS score <16 and full remission as a score <7.
RESULTS: A total of 34.8% of the patients had comorbid major depression and dysthymia at baseline enrollment. Compared with those with major depression alone, they had longer time to both partial (median number of days = 175 versus 106) and full remission (median number of days = 433 versus 244) from major depression. In the repeated measures mixed model predicting MADRS score over 3 years of follow-up and controlling for the effects of potential confounders, the effect of having comorbid dysthymia was not consistent over time, with patients with both disorders having higher predicted scores after initial response.
CONCLUSIONS: Older patients with comorbid major depression and dysthymia have a less favorable trajectory of recovery compared with those with major depression alone.