Mental health from 5 years before to 10 years after bariatric surgery in adolescents with severe obesity: a Swedish nationwide cohort study with matched population controls

Background: The long-term effects of bariatric surgery on the mental health of adolescents with severe obesity remain uncertain. We aimed to describe the prevalence of psychiatric health-care visits and filled prescription psychiatric drugs among adolescents with severe obesity undergoing bariatric surgery in the 5 years preceding surgery and throughout the first 10 years after surgery, and to draw comparisons with matched adolescents in the general population. Methods: Adolescents with severe obesity and who underwent bariatric surgery were identified through the Scandinavian Obesity Surgery Registry. We included adolescents who had bariatric surgery between 2007 and 2017 and were younger than 21 years at time of surgery. Each adolescent patient was matched with ten adolescents from the general population by age, sex, and county of residence. Specialist psychiatric care and filled psychiatric prescriptions were retrieved from nationwide data registers. Findings: 1554 adolescents (<21 years) with severe obesity underwent bariatric surgery between 2007 and 2017, 1169 (75%) of whom were female. At time of surgery, the mean age was 19.0 years [SD 1.0], and the mean BMI was 43.7 kg/m(2) (SD 5.5). 15 540 adolescents from the general population were matched with adolescents in the surgery group. 5 years before the matched index date, 95 (6.2%) of 1535 surgery patients and 370 (2.5%) of 14 643 matched adolescents had a psychiatric health-care visit (prevalence difference 3.7%; 95% CI 2.4-4.9), whereas 127 (9.8%) of 1295 surgery patients and 445 (3.6%) of 12 211 matched adolescents filled a psychiatric drug prescription (prevalence difference 6.2%; 95% CI 4.5-7.8). The year before the matched index date, 208 (13.4%) of 1551 surgery patients and 844 (5.5%) of 15 308 matched adolescents had a psychiatric health-care visit (prevalence difference 7.9%; 95% CI 6.2-9.6), whereas 319 (20.6%) of 1551 surgery patients and 1306 (8.5%) of 15 308 matched adolescents filled a psychiatric drug prescription (prevalence difference 12.0%; 10.0-14.1). The prevalence difference in psychiatric health-care visits peaked 9 years after the matched index date (12.0%; 95% CI 9.0-14.9), when 119 (17.6%) of 675 surgery patients and 377 (5.7%) of 6669 matched adolescents had a psychiatric health-care visit. The prevalence difference in filled psychiatric drug prescription was highest 10 years after the matched index date (20.4%; 15.9-24.9), when 171 (36.5%) of 469 surgery patients and 739 (16.0%) of 4607 matched adolescents filled a psychiatric drug prescription. The year before the matched index date, 19 (1.2%) of 1551 surgery patients and 155 (1.0%) of 15304 matched adolescents had a health-care visit associated with a substance use disorder diagnosis (mean difference 0.2%, 95% CI -0.4 to 0.8). 10 years after the matched index date, the prevalence difference had increased to 4.3% (95% CI 2.3-6.4), when 24 (5.1%) of 467 surgery patients and 37 (0.8%) of 4582 matched adolescents had a health-care visit associated with a substance use disorder diagnosis. Interpretation: Psychiatric diagnoses and psychiatric drug prescriptions were more common among adolescents with severe obesity who would later undergo bariatric surgery than among matched adolescents from the general population. Both groups showed an increase in prevalence in psychiatric diagnoses and psychiatric drug prescriptions leading up to the time of surgery, but the rate of increase in the prevalence was higher among adolescents with severe obesity than among matched adolescents. With the exception of health-care visits for substance use disorders, these prevalence trajectories continued in the 10 years of follow-up. Realistic expectations regarding mental health outcomes should be set preoperatively. Funding: Swedish Research Council, Swedish Research Council for Health, Working Life and Welfare.