A Longitudinal Mediation Analysis of Quality of Life After Metabolic and Bariatric Surgery

ABSTRACT Background and Aim Severe obesity is associated with physical comorbidity and impaired health‐related quality of life (HRQoL). Although metabolic and bariatric surgery (MBS) is generally associated with improvements in HRQoL and mental health, inter‐individual variability is substantial, and the functional mechanisms through which preoperative psychological distress may influence postoperative HRQoL trajectories are incompletely characterized. To provide a clearer mechanistic framework, this study examined whether baseline depressive and anxiety symptoms predict 12‐month HRQoL and whether reductions in functional psychosocial impairment mediate these improvements. Methods Single‐center longitudinal cohort of adults with severe obesity undergoing metabolic and bariatric surgery. Assessments at baseline (T0) and 12 months (T1) included the Patient Health Questionnaire–9 (PHQ‐9), Generalized Anxiety Disorder–7 (GAD‐7), Clinical Impairment Assessment (CIA), and the 36‐Item Short Form Health Survey (SF‐36). Bayesian multilevel mediation models (BMLM) adjusted for sociodemographic and clinical covariates were used. Results Participants ( n = 251; 76.9% women) showed significant reductions in depressive and anxiety symptoms, psychosocial impairment, and BMI from T0 to T1, alongside improvements in all SF‐36 domains ( p < 0.001). Mediation analyses revealed that reductions in psychosocial impairment significantly mediated the relationship between baseline depressive symptoms and HRQoL improvements, explaining up to 42% of the total effect. Anxiety symptoms showed weaker and less consistent mediation. Sensitivity analyses confirmed the robustness of findings across specifications. Conclusion MBS enhances HRQoL and reduces psychological distress. Psychosocial impairment mediates these benefits, especially for depressive symptoms. Integrating psychosocial assessment into pre‐ and postoperative care may help identify vulnerable patients and optimize long‐term outcomes.