Depressive symptoms in subjects with diagnosed and undiagnosed type 2 diabetes

Objective: 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. Methods: 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 ( >= 5.6 and <7.0 mmol/l), undiagnosed DM2 (FPG >= 7.0 mmol/l), and diagnosed DM2. Presence of depressive symptoms was defined as a score of >= 25 on the depression subscale of the Symptom Check List (SCL-90) or self-reported use of antidepressants. Results: 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. Conclusions: 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.