Severity of depression, anxious distress and the risk of type 2 diabetes - A population-based cohort study in Sweden

Background: Previous studies assessing the relationship between depression and diabetes mellitus did not consider the severity of depression. In the present study we assessed the risk of developing type 2 diabetes mellitus (T2DM) among people with various severity of depression. Methods: This prospective longitudinal cohort study included 9,936 individuals residing in Stockholm County, Sweden who responded to the baseline questionnaire in 1998-2000. The participants were followed from 1 year after the baseline up to 2015 for the occurrence of T2DM, using the National Patient Register, Swedish Prescribed Drug Registers, and Cause of Death Register. Depression and anxious distress were assessed using psychiatric rating scales and defined according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Results: Depression was associated with a statistically significant increased risk of T2DM after adjusting for potential confounders (OR 1.48, CI 1.10, 1.99). The strongest association was observed for severe depression (OR 1.72, CI 1.15, 2.59). Further, those with depression, regardless of severity, and with concurrent moderate/severe anxious distress had an increased risk of T2DM (OR 1.73, CI 1.13, 2.63) compared to those with neither depression nor anxious distress. Conclusions: The study adds evidence that depression is associated with a higher risk for developing T2DM, and the association is stronger among people with severe depression.