Diabetes mellitus and risk of subsequent depression: A longitudinal study

BackgroundFindings of previous studies on the association between diabetes and the risk of depression are contradictory. Furthermore, much less is known concerning the association among young adults.ObjectiveTo investigate whether diabetes is associated with an increased risk of subsequent development of depression, with emphasis on age-specific variations.DesignA cohort study.SettingClaims data of one million subjects randomly selected from 23 million people covered by the Taiwan National Health Insurance program.ParticipantsFrom the claims data, we identified 14,048 patients aged ≥20 years with newly diagnosed diabetes in 2000–2002 and randomly selected 55,608 non-diabetic subjects for comparison, that were frequency-matched by calendar year, age, and gender. Incidence rates of depression to the end of 2007 were identified, and risks were compared between the two groups.ResultsThe incidence of depression was 1.80-times higher in the diabetic group than in nondiabetic subjects over a median follow-up of 6.5 years (adjusted hazard ratio [HR] = 1.46, 95% confidence interval [CI]: 1.24–1.71). Age-specific HRs for incidence of depression in relation to diabetes were not statistically different between the patient subgroups aged 20–39, 40–49, 50–59, 60–69 and ≥70 years (p value for age-diabetes interaction = 0.33). Stratified analyses showed that the association was much stronger for subjects without comorbid cardiovascular disease than for those with this comorbidity. Insulin treatment was associated with a 43% reduced risk of depression in diabetic patients.ConclusionsIn this population-based study, diabetic patients were at a higher risk for subsequent depression. Adequate treatment reduced the risk.