Recurrent subthreshold depression in type 2 diabetes: An important risk factor for poor health outcomes

Abstract

OBJECTIVE: To evaluate the association between recurrent subthreshold depressive episodes and functioning in a prospective community sample of people with type 2 diabetes. RESEARCH DESIGN AND METHODS: A prospective community study in Quebec, Canada, was carried out between 2008 and 2013 (n = 1,064). Five yearly follow-up assessments (telephone interviews) were conducted. Baseline and the first three follow-up assessments were used to identify recurrent subthreshold depressive episodes (Patient Health Questionnaire [PHQ]-9). Functioning (World Health Organization Disability Assessment Schedule II [WHODAS-II]) and health-related quality of life (Centers for Disease Control and Prevention [CDC] unhealthy days) at 4- and 5-year follow-up assessments were the outcome measures. RESULTS: Nearly half of the participants suffered from at least one episode of subthreshold depressive symptoms. After adjusting for potentially confounding factors, the risk of poor functioning/impaired health-related quality of life was nearly three times higher (relative risk = 2.86) for participants with four subthreshold depressive episodes compared with participants with no/minimal depression. Results suggest a dose-response relationship: the risk of poor functioning/impaired health-related quality of life increased with the number of recurrent subthreshold depressive episodes even after controlling for potentially confounding variables (significant linear trend, P < 0.001). CONCLUSIONS: Recurrent subthreshold depressive symptoms might be an important risk factor for poor health outcomes in type 2 diabetes. Early identification, monitoring, and treatment of recurrent subthreshold depressive symptoms might improve functioning and quality of life in people with type 2 diabetes. © 2014 by the American Diabetes Association.