The clinical significance of subsyndromal depression in older primary care patients

Objective: Many seniors experience depressive symptoms not meeting standard diagnostic criteria. The authors sought to examine the clinical correlates of older primary care patients with subsyndromal depression (SSD), hypothesizing that SSD subjects have greater symptoms and functional impairment than nondepressed patients, but not as severe as those with major or minor depression, and to explore the characteristics of subjects captured by three different definitions of SSD used in prior published work. Methods: The authors conducted a cross-sectional case comparison study that enrolled 662 primary care patients age >= 65 years. Outcomes were validated measures of psychopathology, medical illness burden, and functional status. Results: All three SSD groups captured patients with greater symptoms and functional impairment than the nondepressed group. SSD subjects were as ill as those with minor or major depression on some measures (e.g., medical burden). Each SSD group definition captured some subjects unique to that group. Conclusions: Sub-syndromal depression is common and associated with symptoms or impairments of clinical importance. Sole reliance on Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition definitions of major or minor depression omits a substantial proportion of seniors with clinically significant depressive symptoms. Longitudinal study is needed to help clinicians identify those at greatest risk for poor outcomes, while researchers testing mechanistic models should include patients with SSD to determine whether they share pathogenetic underpinnings with more severe mood disorders.