Graduation Year


Document Type




Degree Granting Department


Major Professor

William P. Sacco, Ph.D.

Committee Member

Paul B. Jacobsen, Ph.D.

Committee Member

Brent J. Small, Ph.D.


A1c, depression, nephropathy, neuropathy, retinopathy


People with diabetes are at double the risk of developing depression. Depression is associated with increased morbidity and mortality in people with diabetes. Levels of A1c have been linked to microvascular complications (e.g., retinopathy, nephropathy, and neuropathy) as well as depression. The interrelationship between A1c, microvascular complications, and depression has not previously been investigated in a comprehensive model, and a better understanding of the nature of these associations is needed. Preliminary analyses test the assumption that A1c mediates the relationship between group assignment in the Diabetes Control and Complications Trial (DCCT) and microvascular complications. The primary purpose of the study is to examine multiple mediation models, which hypothesize that the severity of microvascular complications mediates the relationship between A1c and depressive symptomatology levels. Participants were people with type 1 diabetes (N = 1441) enrolled in the DCCT, a longitudinal randomized controlled trial investigating intensive insulin treatment and diabetes complications, and divided into primary (e.g., no retinopathy) and secondary (e.g., mild retinopathy) cohorts. Biological markers were used to measure A1c and microvascular complications. Depressive symptomatology was measured by the depression subscale of the Symptom Checklist-90-Revised. Simple and multiple mediation analyses were used to test proposed models. A1c mediates the relationship between DCCT group assignment and microvascular complications. Microvascular complications partially mediate the relationship between A1c and depression for the full sample and secondary cohort. Results support the hypothesis that the severity of microvascular complications, in part, accounts for the association between A1c and depressive symptomatology in people with type 1 diabetes.