Increased risk for major depressive disorder in severely obese patients after bariatric surgery - a 12-year nationwide cohort study.

BACKGROUND: Bariatric surgery is associated with a significant improvement in depressive mood in the initial postoperative years, but the maintenance of the improvement is under debate.

AIM: To explore the association between bariatric surgery and major depressive disorder (MDD) in a 12-year nationwide cohort study.

METHOD: Using the National Health Insurance Research Database of Taiwan, we identified 2302 patients who underwent bariatric surgery in 2001-2009. These patients were matched by propensity score to 6493 obese patients who did not receive bariatric surgery. We followed the surgical and control cohorts until death, any diagnosis of MDD or 31 December 2012. We used Cox proportional hazard regression models to calculate the relative risk of MDD in those who received bariatric surgery.

RESULTS: Overall, there was a 1.70-fold (95% CI: 1.27-2.27) higher risk of MDD in the surgical group. Subjects receiving malabsorptive procedures showed a higher risk of MDD (3.01, 95% CI: 1.78-5.09) than those receiving restrictive procedures (1.51, 95% CI: 1.10-2.07). Stratified by follow-up period, there was a higher risk of MDD in the surgical group (2.92, 95% CI: 1.75-4.88) than in the restrictive group four years after bariatric surgery.

CONCLUSIONS: Bariatric surgery was significantly associated with an elevated risk of MDD. KEY MESSAGES Bariatric surgery is associated with a significant improvement in depressive mood in the initial postoperative years, but the improvement is not maintained. Less is known about the relationship between bariatric surgery and risk of major depressive disorder. This was the first nationwide cohort study which found that bariatric surgery was significantly associated with an elevated risk of MDD (aHR: 1.70; CI: 1.27-2.27), mainly with malabsorptive procedures (aHR: 3.01; CI: 1.78-5.09) and at time points more than four years after surgery (aHR: 2.92; CI: 1.75-4.88) compared with the risk in matched controls. These findings imply an association between long-term malabsorption and the postoperative incidence of MDD. Long-term malabsorption might be related to the incidence of major depressive disorder after bariatric surgery. The possible causal relationship between nutritional deficiency after bariatric surgery and major depressive disorder warrants further investigation.