The relationship of depression and diabetes: pathophysiological and treatment implications

Diabetes is a highly prevalent, chronic disease that requires ongoing, multi-specialty medical care combined with patient self-management, family support, and education to prevent or delay end-organ morbidity and mortality. There is clearly an increased prevalence of major depressive disorder, a relatively common and costly central nervous system syndrome, in diabetic patients. During the past two decades, multiple studies reveal that not only are depressive symptoms a risk factor for the development of type 2 diabetes, but they have also been shown to contribute to hyperglycemia, diabetic complications, functional disability and all-cause mortality among diabetic patients. This article reviews studies examining the relationship between depression and diabetes, neurochemical underpinnings of the two disorders, and the diagnosis and treatment of depression associated with diabetes. We examine the validity of rating scales used to diagnose depression in diabetic patients and review the literature on psychotherapeutic and psychopharmacologic management for these patients. The challenges of optimal depression screening and treatment in primary care settings of diabetic patients are currently under close scrutiny, especially regarding their potential impact related to improvements in diabetes-related outcomes and decreased health care costs, be it "depression" or "diabetes" relevant. Much of the current literature regarding the intertwined nature of diabetes and depression is cross-sectional in nature. Future research should focus on longitudinal, prospective studies to determine causal factors. What is clear from the research reviewed in this article is that depression and diabetes should be treated together rather than as isolated diseases. The mind/body dualism is a false dichotomy and a truly team-based approach is necessary to address both issues of depression and diabetes. Collaborative care and the "patient-centered medical home" have emerged as potentially effective interventions to improve quality of care and patient outcomes in patients with depression and medical illnesses such as diabetes.