Association between medical comorbidity and treatment outcomes in late-life depression

Previous studies have demonstrated an association between major depression and physical disability in late life. The objectives of this study were to examine the relationship between specific medical illnesses and the outcomes of treatment for late-life depression.

The study was a longitudinal assessment of medical illness, depression, and disability. Patients were assessed during an initial inpatient psychiatric hospitalization and 3 months postdischarge.

All patients were initially evaluated after admission to one of 71 inpatient psychiatric treatment facilities.

A sample of 671 older patients who received inpatient treatment for depression was evaluated at entry into the hospital and 3 months after discharge.

Depressive symptoms were measured using the Geriatric Depression Scale. Disability was measured using the instrumental activities of daily living scale and the Medical Outcomes Study 36-item short form. Medical illness was assessed using the medical illness checklist.

As previously reported, physical disability and the total number of medical illnesses were significantly related to change in depressive symptoms. In this study, we find that arthritis, circulatory problems, a speech disorder, or a skin problem, but not other general medical conditions, were related to a worse outcome with respect to depression symptoms. The effect of these problems was statistically and clinically significant. After controlling for pretreatment disability, arthritis and skin problems continued to predict a worse outcome. However, the apparent effect of each of these conditions was mediated by the residual disability after treatment.

The results of this study support the hypothesis that certain somatic disorders play a role in the treatment response of late-life depression and suggest that the effect of specific illnesses on depression may be mediated by the presence of functional disability.