Depression Among Individuals with Irritable Bowel Syndrome: A Nationwide Claims-Based Analysis of 3.9 Million Koreans

Background/Objectives: While a growing body of research indicates an increased psychiatric burden, including depression comorbidity, among individuals with irritable bowel syndrome (IBS), evidence from large claim-based databases remains limited. This study aimed to investigate the association between IBS and depression among a nationally representative sample of 3.9 million Korean adults. Methods: We used data from the 2021 Korean National Health Insurance Service (NHIS), including a total of 3,864,586 individuals aged 19-64 years who participated in the national biennial health screening exam between 1 January 2021 and 31 December 2021. Exposures and outcomes were identified based on the International Classification of Diseases, Tenth Revision (ICD-10), codes: F32 and F33 for depression and K58 for IBS. Multivariable logistic regression analysis adjusted for age, sex, residential area, comorbidity, smoking, alcohol use, physical activity, and body mass index was conducted. Results: One-year prevalence of depression among the entire sample was 4.0%. The prevalence among individuals with IBS (7.3%) was significantly higher than that among those without IBS (3.6%, p < 0.001). Multivariable logistic regression analysis confirmed this relationship (OR = 1.77, 95% CI: 1.74, 1.79) after adjusting for all covariates. Conclusions: Our findings suggest that individuals with IBS are vulnerable to depression, emphasizing the need for integrated approaches in clinical management and public health policy responding to the rising burden of IBS.