Does treatment of subsyndromal depression improve depression-related and diabetes-related outcomes? A randomised controlled comparison of psychoeducation, physical exercise and enhanced treatment as usual

Background: Elevated depressive symptoms that do not reach criteria for a clinical diagnosis of depression are highly prevalent in persons with diabetes. This study was aimed at determining the efficacy of psychoeducation and physical exercise compared with enhanced treatment as usual on 1-year changes in depressive symptoms, diabetes distress and self-management, and quality of life and metabolic control in type 2 diabetes patients with subsyndromal depression. Methods: Adult type 2 diabetes patients who screened positively for depression and expressed a need for professional help with mood-related issues were eligible. Exclusion criteria were clinical depression, current psychiatric treatment and advanced diabetes complications. Out of 365 eligible patients 209 consented to either 6 weekly sessions of psychoeducation (A) and physical exercise (B), or to enhanced treatment as usual (C). Computer-generated sequences for block randomisation stratified by gender were used. Depressive symptoms (primary outcome) and diabetes distress, diabetes self-care, metabolic control and health-related quality of life (secondary outcomes) were analysed at 6-month and 12-month follow-up using repeated-measures ANOVAs. Results: Out of the 74 patients randomised into group A, 66 into B and 69 into group C, 203 completed the interventions, and 179 patients with all 3 assessments were analysed. Depressive symptoms in participants from the psychoeducational, physical exercise and the enhanced treatment as usual groups improved equally from baseline to 12-month follow-up (time versus time x group effect; F = 12.51, p < 0.001, eta(2) = 0.07 and F = 0.609, p = 0.656, eta(2) = 0.007 respectively), as did diabetes distress and quality of life (all p < 0.001), diabetes self-care (p < 0.001 to < 0.05), triglycerides, and total cholesterol and LDL-cholesterol (p < 0.001). Conclusions: The employed interventions had comparable positive effects on 12-month psychological and diabetes-related outcomes suggesting that even minimal intervention addressing patients' diabetes-related problems and concerns had favourable clinical implications and might be sufficient to treat subsyndromal depression. Further investigation is warranted to clarify possible mechanisms of improvement.