Depressive symptoms in subjects with diagnosed and undiagnosed type 2 diabetes

To investigate if disturbed glucose homeostasis or known diagnosis of diabetes was associated with depressive symptoms. The reason for the increased prevalence of depression in patients with Type 2 diabetes mellitus (DM2) is unknown.

Within the Utrecht Health Project, an ongoing longitudinal study among inhabitants of a residential area of a large city in The Netherlands, 4747 subjects (age: 39.4 +/- 12.5 years) were classified into four mutually exclusive categories: normal fasting plasma glucose (FPG) (<5.6 mmol/l), impaired FPG (> or =5.6 and <7.0 mmol/l), undiagnosed DM2 (FPG > or =7.0 mmol/l), and diagnosed DM2. Presence of depressive symptoms was defined as a score of > or =25 on the depression subscale of the Symptom Check List (SCL-90) or self-reported use of antidepressants.

Diagnosed DM2 was associated with an increased risk of depressive symptoms (odds ratio (OR) = 1.69; 95% confidence interval (CI) 1.06-2.72) after adjustment for demographic and lifestyle variables. Additional adjustment for number of chronic diseases reduced the OR to 1.36 (95% CI 0.83-2.23). Impaired fasting glucose and undiagnosed DM2 were not associated with depressive symptoms.

Our findings suggest that disturbed glucose homeostasis is not associated with depressive symptoms. The increased prevalence of depressive symptoms among patients with diagnosed DM2 suggests that depressive symptoms might be a consequence of the burden of diabetes. The number of chronic diseases seems to explain part of the association between DM2 and depressive symptoms.