Background. In patients with chronic medical conditions, depression can be viewed as an expected reaction to illness or an independent condition requiring active treatment. We examine how clinical and functional outcomes of depression treatment compare in primary-care patients with and without chronic medical illness.

Method. Health plan administrative data were used to identify primary-care patients initiating antidepressant treatment, including a general sample (n=204) and cohorts with ischemic heart disease (n=68), diabetes (n=93), or obstructive lung disease (n=74). Telephone interviews at baseline, 2 months, and 6 months assessed depression (Structured Clinical Interview for DSM-IV, Hopkins Symptom Checklist depression scale), functional status (SF-36) and days of disability because of to illness.

Results. At baseline, depression severity in patients with diabetes and obstructive lung disease was similar to those without medical co-morbidity, but significantly lower in those with ischemic heart disease. Social and emotional functioning were similar across all groups, but those with chronic medical illness reported greater physical impairment. All groups showed significant improvement in depression over six months, but the rate of improvement was significantly slower in those with heart disease. All groups showed significant and similar improvement in social and emotional functioning, but physical functioning showed little change. Days of disability and restricted activity improved significantly in all groups. Improvement in depression during treatment was strongly related to change in disability.

Conclusions. Patients with chronic medical illness and co-morbid depression show significant improvements in mood, social and emotional functioning, and disability following initiation of depression treatment. Depression may be a stronger determinant of disability than is stable chronic medical illness.