New Evidence Added to Strong Connection Between Depression and Diabetes Outcomes

Nearly a quarter of all patients with diabetes also have depression, and up to 12% of diabetes patients experience major depressive disorder. The presence of depression not only has major impacts on patients’ quality of life, it also has been shown to be associated with poorer glycemic control and complications of diabetes. While this connection is well-established, the causal pathways remain incompletely understood. Though it makes sense that patients with depression are less likely to exhibit good self-care, this effect doesn’t fully account for poor diabetes control.

A new retrospective analysis in Diabetes Therapy(funded by Eli Lilly and performed by clinicians associated with Eli Lilly) investigated associations between depression parameters and glycemic control using data from a 24—month, prospective, observational, non–interventional study evaluating glycemic response following insulin initiation for type 2 diabetes mellitus (T2DM). The analysis found that patients with higher depression parameters or distress at baseline had significantly higher rates of microvascular complications at baseline and higher glycated hemoglobin (HbA1c) levels.

The connection between diabetes and depression is important because “psychological insulin resistance,” under which patients are reluctant to start insulin therapy for a variety of reasons, can be exacerbated by depression. The connection can be hard to establish because depression can be difficult to measure. This study measured depression by history of diagnosis depression; depressed mood as determined by a patient self-report; and diabetes distress as determined by a survey.

The analysis found consistent and significant associations between poorer glycemic control and each of the three depression and distress parameters.It further showed that patients with depressive symptoms were significantly more likely than patients without the depression parameter to be female, to have a higher BMI, and to have microvascular complications. In addition, patients with depressed mood had a significantly longer duration of diabetes than patients without depressed mood.

The study authors concluded, “History of diagnosed depression, diabetes-related distress, and depressed mood were associated with a higher rate of microvascular complications. Diagnosed depression and diabetes-related distress also showed higher HbA1c at baseline when insulin was initiated. Insulin therapy improved glycemic control, while preexisting depressed mood declined and diabetes-related distress remained unchanged.”

Limitations of the study include the ad-hoc nature of the study and the fact that none of the measures used in the analysis were developed or validated for use as a stand-alone measure of depression. Another limitation relates to the lack of characterization of the type of depression the patients suffered with or whether or not they were taking antidepressants at baseline.

The study suggests that removing the barriers associated with insulin can improve both depressed mood and glycemic control. “A better understanding of the relationship between glycemic control, diabetic complications, and specific affective parameters may help clinicians to focus more attention on screening for affective conditions and provide information that may lead to more timely treatment or referrals to both mental health and diabetes professionals,” the authors note.