The impact of psychiatric comorbidity on weight loss after bariatric surgery a 2-year register-based follow-up cohort study

Background and objectives: Although most patients achieve substantial weight loss after bariatric surgery, outcomes vary, and predictors of sustained long-term weight loss remain unclear. This study examined whether preexisting mental disorders influence postoperative weight loss. Setting and methods: We used data from the Central Denmark Region's electronic health record system (2012-2021) including all public bariatric surgeries. Patients were categorized by psychiatric history based on diagnosis and medication use. Groups were compared regarding baseline characteristics, surgery type, change in body mass index (ΔBMI), and weight trajectories from one year before to two years after surgery. Results: Among 1846 patients, 21% had a mental disorder. Baseline BMI, lipid levels, HbA1c, and surgery type were similar between groups. Patients with mental disorders were slightly younger and more often female. Mood and anxiety disorders were most prevalent. Weight loss was comparable between groups. Missing postoperative weight data occurred in 6% of patients with mental disorders and 5% without. By two years, 30% in both groups lacked weight data. No differences were observed in HbA1c or lipid levels. Conclusion: Patients with and without mental disorders achieve comparable short-term weight loss and metabolic outcomes after bariatric surgery. Psychiatric comorbidity may not preclude favorable surgical outcomes when patients are appropriately selected and supported. However, the absence of formal preoperative psychological evaluation and lack of psychosocial outcome measures limit interpretation of the study findings. Further studies should assess long-term outcomes, including mental health and quality of life.