Objective: 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.
Design and participants: Cross-sectional design involving adults diagnosed with Type 2 diabetes (N = 99).
Main outcome measures: 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).
Results: 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.
Conclusion: 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.
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