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

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

Methods: 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.

Results: 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.

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