Psychiatric Manifestations after Sleeve Gastrectomy and Their Relationship with Nutritional Deficiencies: A Retrospective Cohort Study

Abstract Background Psychiatric morbidity may occur after sleeve gastrectomy (SG), and micronutrient deficiencies may contribute. This study evaluated new-onset psychiatric disorders after SG and their association with postoperative nutritional deficiencies. Methods This retrospective cohort study included 50 patients with BMI ≥ 35 kg/m² who underwent laparoscopic SG between August 2023 and August 2025 and completed at least 6 months of follow-up. Patients with preoperative psychiatric illness were excluded. Psychiatric diagnoses were established using Structured Clinical Interview for DSM Disorders. Vitamin D, vitamin B12, thiamine, folate, and iron were assessed. Associations were evaluated using Fisher's exact test, odds ratios (ORs) with 95% CIs, and univariable binary logistic regression. Results Eight patients (16%) developed a psychiatric disorder: depression in 6 (75%), anxiety disorder in 1 (12.5%), and binge-eating disorder in 1 (12.5%). Patients with psychiatric disorders had lower serum folate (5.1 ± 3.7 vs 11.3 ± 3.6 ng/mL; P = 0.002) and thiamine (79.9 ± 25.7 vs 117.6 ± 31.5 nmol/L; P = 0.004). Thiamine deficiency (OR 13.44, 95% CI 2.56–70.58; P = 0.003) and vitamin B12 deficiency (OR 5.54, 95% CI 1.21–25.38; P = 0.030) were associated with psychiatric disorders. All patients with folate deficiency had psychiatric manifestations (P < 0.001), although OR was not estimable. Lower thiamine and folate levels were associated with psychiatric disorders. Conclusions New-onset psychiatric disorders occurred in 16% of patients during follow-up. Lower postoperative thiamine and folate levels and deficiencies of thiamine and vitamin B12 were associated with psychiatric morbidity. These findings support nutritional and psychiatric surveillance after SG, while larger prospective studies are needed to clarify causality.