The Netherlands Study of Depression and Anxiety (NESDA) is a multi-site naturalistic cohort study to: (1) describe the long-term course and consequences of depressive and anxiety disorders, and (2)

Depression is common in later life. Methodological differences between studies preclude firm conclusions about cross-cultural and geographical variation. Improving the comparability of epidemiological research constitutes an important step forward.

Aims/hypothesis: Evidence strongly suggests that depression and type 2 diabetes are associated, but the direction of the association is still unclear. Depression may occur as a consequence of having diabetes, but may also be a risk factor for the onset of type 2 diabetes. This study examined the latter association by reviewing the literature and conducting a meta-analysis of longitudinal studies on this topic. Methods: Medline and PsycInfo were searched for articles published up to January 2005. All studies that examined the relationship between depression and the onset of type 2 diabetes were included. Pooled relative risks were calculated using fixed and random effects models. To explore sources of heterogeneity between studies, subgroup analyses and meta-regression analyses were performed. Results: Nine studies met our inclusion criteria for this meta-analysis. The pooled relative risk was 1.26 (1.13-1.39) using the fixed effects model and 1.37(1.14-1.63) using the random effects model. Heterogeneity between studies could not be explained by (1) whether studies controlled for undetected diabetes at baseline; (2) the method of diabetes assessment at followup; (3) the baseline overall risk of diabetes in the study population; and (4) follow-up duration. Conclusions/ interpretation: Depressed adults have a 37% increased risk of developing type 2 diabetes mellitus. The pathophysiological mechanisms underlying this relationship are still unclear and warrant further research. A randomised controlled study is needed to test whether effective prevention or treatment of depression can reduce the incidence of type 2 diabetes and its health consequences.

The EURO-D scale should permit valid comparison of risk-factor associations between centres, even if between-centre variation remains difficult to attribute.

Depression seems to be an independent risk factor for the onset of a wide range of CVDs, although this evidence is related to a high level of heterogeneity.