Diabetes mellitus as a risk factor for depression. A meta-analysis of longitudinal studies

The present meta-analysis is aimed at the assessment of the risk of incident clinical depression and/or depressive symptoms in patients with diabetes.

A Medline search was performed on December 30th, 2011, using the search string: "diabetes AND (depression OR antidepressant)", selecting longitudinal studies that assessed the risk of incident depression in subjects with or without diabetes. Study design and characteristics were verified for each study. A meta-analysis was performed for unadjusted and adjusted risk ratios of incident depression in subjects with diabetes using a random effect model. Additional analyses were performed to assess heterogeneity, publication bias and specific hazard ratios for several possible confounders.

Of the 1898 retrieved studies, 16 were included in the meta-analysis, enrolling 497,223 subjects, with a mean follow-up of 5.8 years and 42,633 cases of incident depression. A higher incidence of depression was found in diabetic subjects (1.6% vs 1.4% yearly), with unadjusted and adjusted risk [95% confidence interval] of 1.29 [1.18-1.40] (p<0.001) and 1.25 [1.10-1.44] (p=0.001), respectively.

Diabetes is associated with a significantly increased risk for depressive symptoms. Pathogenetic mechanisms connecting diabetes with depression deserve further exploration.