Persons with treated type 2 diabetes are at increased risk for developing depression, while a more modest association was found between persons with depression and the risk of diabetes, according to a study in the June 18 issue of JAMA.
The prevalence of clinical depression and the presence of elevated depressive symptoms are higher among persons with diabetes compared with the general population. These associations may be related to increased risk of depressive symptoms in individuals with diabetes, increased risk of type 2 diabetes in individuals with depressive symptoms, or both. It is unclear whether type 2 diabetes is a risk factor for increased symptoms of depression. "A diagnosis of diabetes or the burden of dealing with its complications might also lead to symptoms of depression," the authors write.
Sherita Hill Golden, M.D., M.H.S., of Johns Hopkins University, Baltimore, and colleagues used measures of fasting blood glucose and depressive symptoms to test whether elevated depressive symptoms predicted incident type 2 diabetes and whether participants with type 2 diabetes at the beginning of the study were more likely to develop increased symptoms of depression than participants without diabetes. The study included men and women age 45 to 84 years who enrolled in 2000-2002 and were followed up until 2004-2005. Elevated depressive symptoms were defined by high scores on the Center for Epidemiologic Studies Depression Scale (CES-D; a questionnaire given to participants), use of anti-depressant medications, or both. Participants were categorized as having normal fasting glucose, impaired fasting glucose or type 2 diabetes.
Analysis 1 included 5,201 participants without type 2 diabetes at baseline and estimated the relative risk of incident type 2 diabetes over 3.2 years for those with and without depressive symptoms. Analysis 2 included 4,847 participants without elevated depressive symptoms at baseline and calculated the relative odds of developing depressive symptoms over 3.1 years for those with and without type 2 diabetes.
The researchers found that treated type 2 diabetes was associated with a 52 percent higher risk of developing elevated depressive symptoms. Individuals with untreated type 2 diabetes were not at increased risk.
In examining the development of type 2 diabetes among individuals with and without elevated depressive symptoms, the incidence of type 2 diabetes over 3.2 years was 22.0 per 1,000-person years for those with elevated depressive symptoms and 16.6 for those without elevated depressive symptoms. Thus, there was a significant association between higher levels of symptoms of depression and incident diabetes; however, the association was no longer statistically significant following adjustment for lifestyle factors.
"Our findings of an association in participants with treated but not untreated type 2 diabetes suggests that the psychological stress associated with diabetes management may lead to elevated depressive symptoms," the authors write. Regarding the link between depression and the development of diabetes, "depressive symptoms are associated with several metabolic and behavioral risk factors for type 2 diabetes. ... depressed individuals are less likely to comply with dietary and weight loss recommendations and more likely to be physically inactive, contributing to obesity, a strong risk factor."
"... the present study contributes to a growing body of literature indicating a bidirectional association between these 2 serious long-term diseases. Future studies should determine whether interventions aimed at modifying behavioral factors associated with depression will complement current type 2 diabetes prevention strategies. Finally, these findings suggest that clinicians should be aware of increased risk of elevated depressive symptoms in individuals with treated type 2 diabetes and consider routine screening for depressive symptoms among these patients," the authors conclude.
(JAMA. 2008;299:2751-2759. Available pre-embargo to the media at www.jamamedia.org)
Editor's Note: Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.