The Complex Association Between Bariatric Surgery and Depression: a National Nested-Control Study

Background Although bariatric surgery has been shown to reduce weight loss and obesity-related conditions, an improvement in depression remains unclear. The aim of this study was to determine whether bariatric surgery is associated with a resolution of depression, and the prevention of its onset. Method Patients with a BMI >= 30 kg/m(2) who had undergone bariatric surgery were identified from the Clinical Practice Research Datalink (CPRD), matched 5:1 to controls. Cox regression analysis was used to determine the risk of developing de novo depression. Kaplan-Meier analysis compared the proportion of patients with no further consultations related to depression between the two groups. Results In total, 3534 patients who underwent surgery, of which 2018 (57%) had pre-existing depression, were matched to 15,480 controls. Cox proportional hazard modelling demonstrated surgery was associated with a HR of 1.50 (95% CI 1.32-1.71, p < 0.005) for developing de novo depression. For those with pre-existing depression, by 5 years, just over 20% of post-surgical patients had no further depression episodes compared with 17% of controls. Conclusion In individuals with a history of depression, bariatric surgery is associated with an improvement in mental health. On the contrary, the finding of increased de novo diagnoses of depression following surgery indicates the need for further study of the mechanisms by which bariatric surgery is associated with depression in this subset of patients.