Diabetes mellitus and risk of subsequent depression: A longitudinal study

Background: Findings 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. Objective: To investigate whether diabetes is associated with an increased risk of subsequent development of depression, with emphasis on age-specific variations. Design: A cohort study. Setting: Claims data of one million subjects randomly selected from 23 million people covered by the Taiwan National Health Insurance program. Participants: From 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. Results: The 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. Conclusions: In this population-based study, diabetic patients were at a higher risk for subsequent depression. Adequate treatment reduced the risk.