Associations between body weight change and incidence of major depressive disorder in patients with type 2 diabetes mellitus: a nationwide longitudinal follow-up cohort study of 1.1 million

Background. Comorbid depression substantially affects the management of glycemia and diabetes-related complications among patients with type 2 diabetes mellitus. In this study, we sought to determine the association between weight change over 4 years and depression risk among patients with type 2 diabetes mellitus. Methods. This population-based retrospective cohort study from the National Health Insurance Services of Korea included 1 111 345 patients with type 2 diabetes who were divided into groups according to body weight change over 4 years. Body weight changes were compared with the preceding 4-year period (2005-2008). Depression was defined according to the International Classification of Diseases 10th revision code for depression (F32 and F33) on one or more inpatient or outpatient claims. Results. During a median follow-up of 7.4 years, 244 081 cases of depression were identified. We observed a U-shaped association between body weight change and depression risk with a higher risk among both groups of weight loss (hazard ratio (HR) 1.17, 95% CI 1.15-1.19 for >= -10%; HR 1.07, 95% CI 1.06-1.08 for -10 to -5%) and weight gain (HR 1.06, 95% CI 1.04-1.08 for >= 10%; HR 1.02, 95% CI 1.01-1.04 for 5-10%) compared with the stable weight group (-5 to 5%). Conclusions. A U-shaped association between body weight change and depression risk was observed in this large nationwide cohort study. Our study suggests that patients with type 2 diabetes and weight change, either gain or loss, could be considered a high-risk group for depression.