Evidence indicates that depression is linked to the development and worsening of diabetes, but the mechanisms underlying this link are not well understood. The authors examined the hypothesis that diabetes-related symptoms mediate the effect of both behavioral adherence and body mass index (BMI) on depression. In addition, they examined whether a prior finding that self-efficacy mediates the effect of behavioral adherence and BMI on depression would replicate with a larger sample size (W. P. Sacco, K. J. Wells, C. A. Vaughan, A. Friedman, S. Perez, & R. Morales, 2005). Also, the relative contributions of diabetes-related symptoms and self-efficacy to depression were evaluated.
Cross-sectional design involving adults diagnosed with Type 2 diabetes (N = 99).
The primary outcome measure was depression (Patient Health Questionnaire: Nine Symptom Depression Checklist). Predictors of depression were diet and exercise adherence (Summary of Diabetes Self-Care Activities Questionnaire), diet and exercise self-efficacy (Multidimensional Diabetes Questionnaire), diabetes symptoms (Diabetes Symptom Checklist), and BMI (based on height and weight data from medical records).
Path and mediation analyses indicated that adherence and BMI each contributed to depression indirectly, via their effects on self-efficacy and diabetes-related medical symptoms.
Results provide evidence consistent with two independent pathways by which BMI and adherence could increase depression in people with Type 2 diabetes. The first pathway indicates that the effects of higher BMI and poor adherence on depression are mediated by lower self-efficacy perceptions. The second pathway indicates that the effect of higher BMI on depression is mediated by increased diabetes symptoms.