Depression in Diabetes: Have We Been Missing Something Important?

An extensive literature has developed to suggest that depression is more common in patients with diabetes than in the general population (1) and is associated with chronic hyperglycemia (2), risk for diabetes complications (3), and mortality (4). Although the causal linkages among these relationships have not been demonstrated, their consistency has led to calls for intensive efforts to identify and treat clinical depression in patients with diabetes, with the reasonable presumption that this will contribute to better diabetes outcomes. Recent studies, however, suggest a more complicated picture and cast doubt on this presumption. Although research has suggested that the prevalence of clinical depression, or major depressive disorder (MDD), among adults with diabetes may be two to three times greater than among community adults (1), recent studies—which have used structured clinical interviews, the gold standard in the diagnosis of MDD— suggest that it is only about 60% more common (5). More importantly, diabetesrelated distress, or significant negative emotional reactions to the diagnosis of diabetes, threat of complications, selfmanagement demands, unresponsive providers, and/or unsupportive interpersonal relationships, has been found to be far more common, more chronic, and more closely related to diabetes self-care and glycemic control than MDD (5–7). Symptoms of depression, such as depressed mood, diminished interest, loss of energy, and concentration difficulties, that are elevated but do not meet severity criteria for MDD (referred to here as depressive symptoms) are also quite common among patients with diabetes and are associated with poor self-care (8). Furthermore, increased risk of complications and early mortality is not limited to those with MDD but also extends to those with elevated depressive symptoms, even when these elevations are quite modest (4). This suggests an incremental relationship between the severity of depressive symptoms and poorer diabetes outcomes rather than an effect of MDD per se. There is minimal evidence for a longitudinal relationship between MDD and hyperglycemia over time, and changes in one over time do not appear to be associated with changes in the other (7). Numerous treatment studies have shown positive effects for the improvement of MDD in diabetic patients, but evidence for resulting glycemic benefit is, at best, weak (9). The current commentary seeks to shed light on the discontinuity among these findings. First, we suggest that there has been considerable confusion among MDD, diabetes-related distress, and depressive symptoms. We argue that this confusion has been exacerbated by measurement problems that stem from the lack of a clear distinction between MDD and nonpsychiatric emotional distress. Second, we suggest that this has led to a narrow focus on potential intervention approaches, originally developed for MDD, that may be limited in their ability to address diabetes-related distress and depressive symptoms. Although we do not deny the importance of true psychiatric presentations of MDD among those with diabetes, traditional approaches to MDD treatment may be unlikely to improve diabetes outcomes unless they also incorporate strategies to address important relationships between MDD and chronic illness (rev. in 10). Finally, we suggest an alternative approach to understanding the common experience of emotional distress in diabetes that emphasizes the demanding experience of diabetes and requires diabetes-specific measurement and treatment approaches.