Outcomes of minor and subsyndromal depression among elderly patients in primary care settings

Background: Although depressive conditions in later life are a major public health problem, the outcomes of minor and subsyndromal depression are largely unknown. Objective: To compare outcomes among patients with minor and subsyndromal depression, major depression, and no depression, and to examine putative outcome predictors. Design: Cohort study. Setting: Patients from primary care practices in greater New York City, and Philadelphia and Pittsburgh, Pennsylvania. Patients: 622 patients who were at least 60 years of age and presented for treatment in primary care practices that provided usual care in a randomized, controlled trial of suicide prevention. Of the 441 (70.9%) patients who completed 1 year of follow-up, 122 had major depression, 205 had minor or subsyndromal depression, and 114 did not have depression at baseline. Measurements: One year after a baseline evaluation, data were collected by using the following tools: Hamilton Depression Rating Scale, the depressive disorders section of the Structured Clinical Interview for DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, fourth edition), Charlson Comorbidity Index, Multilevel Assessment Instrument for measuring instrumental activities of daily living, Physical Component Summary of the Medical Outcomes Study Short Form-36, and Duke Social Support Index. Results: Patients with minor or subsyndromal depression had intermediate depressive and functional outcomes. Mean adjusted 1-year Hamilton depression score was 10.9 (95% CI, 9.6 to 12.2) for those with initial major depression, 7.0 (CI, 5.9 to 8.1) for those with minor or subsyndromal depression, and 2.9 (CI, 1.6 to 4.2) for those without depression (P < 0.001 for each paired comparison). Compared with patients who were not depressed, those who had minor or subsyndromal depression had a 5.5-fold risk (CI, 3.1-fold to 10.0-fold) for major depression at 1 year after controlling for demographic characteristics (P < 0.001). Cerebrovascular risk factors were not associated with a diagnosis of depression at 1 year after controlling for overall medical burden. Initial medical burden, self-rated health, and subjective social support were significant independent predictors of depression outcome. Limitations: Participants received care at practices that had personnel who had been given enhanced education about depression treatment; 29.1% of participants withdrew from the study before completing 1 year of follow-up. Conclusions: The intermediate outcomes of minor and subsyndromal depression demonstrate the clinical significance of these conditions and suggest that they are part of a spectrum of depressive illness. Greater medical burden, poor subjective health status, and poorer subjective social support confer a higher risk for poor outcome.