Depression is a frequent co-morbid condition in diabetic patients. In controlled studies 9% fulfilled criteria for major depression and 26% reported elevated depressive symptoms. Depression rates are twofold higher in diabetic patients than in the non-diabetic population (major depression 5%; elevated depressive symptoms 14%). Diabetes specific risk factors like occurrence of complications, poor glycaemic control, insulin therapy in type 2 diabetic patients are statically associated with elevated depression rates. Furthermore the presence of depressive symptoms in non-diabetic subjects is associated with a significant higher diabetes risk in the future.

Depression in diabetic patients is linked with poorer diabetes self care behaviour like adherence to medication, keeping a healthy diet and physical exercise. The co-morbidity of diabetes and depression has also a negative impact on quality of life, which is greater than the comorbidty of depression and other chronic somatic diseases. Longitudinal studies indicate that depression in diabetes is related to a poorer prognosis. The risk for the development of complications is significantly higher in depressed than in non-depressed diabetic patients. Representative studies showed a significantly higher mortality in diabetic patients with depression than in non-depressed diabetic patients (hazard ratios between 1.67 to 2.6). The results also suggest that these negative consequences of depression are not only present in diabetic patients with severe forms of depression but also in patients with rather mild depression. In summary epidemiological findings imply that depression in diabetes is an important clinical condition warranting clinical attention as well as scientific interest.