Clinical Impact of the Temporal Relationship between Depression and Type 2 Diabetes: The Fremantle Diabetes Study Phase II

Background: The clinical features of type 2 diabetes may differ depending on whether first depression episode precedes or follows the diagnosis of diabetes. Methods: Type 2 patients from the observational community-based Fremantle Diabetes Study Phase II underwent assessment of lifetime depression using the Brief Lifetime Depression Scale (developed and validated for this study) supplemented by information on current depression symptoms (Patient Health Questionnaire, 9-item version) and use of antidepressants. Patients were categorized as never depressed (Group 1), having had depression before diabetes diagnosis (Group 2), diagnosed with depression and diabetes within 2 years of each other (Group 3) and having depression after diabetes diagnosis (Group 4). Results: Of 1391 patients, 20.8% were assigned to Group 2, 6.0% to Group 3 and 14.5% to Group 4. In Group 2, depression occurred a median 15.6 years before diabetes onset at age 37.2+/-14.7 years. These patients had similar clinical characteristics to never depressed patients except for reduced self-care behaviours and having more symptomatic peripheral arterial disease. In Group 4, depression occurred a median 9.9 years after diabetes onset at age 59.8+/-13.0 years. These patients had long duration diabetes, poor glycaemic control, more intensive management and more diabetic complications. Group 4 patients had more current depression than Group 2 but were less likely to be receiving antidepressants. Conclusions/Interpretation: The clinical features of depression and type 2 diabetes are heterogeneous depending on their temporal relationship. There may be corresponding differences in the pathogenesis of depression in diabetes that have implications for diagnosis and management.