Bidirectional associations between irritable bowel syndrome and psychological distress: a longitudinal population-based study

Background Irritable bowel syndrome (IBS) commonly co-occurs with psychological distress, including depression and anxiety, but the temporal and bidirectional nature of this relationship remains unclear. Dysregulation of the gut–brain–microbiota axis has been proposed as a shared mechanism. Methods We conducted two retrospective, population-based cohort studies using Taiwan’s National Health Insurance Research Database (2000–2015). Cohort 1 assessed the risk of incident IBS among patients with newly diagnosed depression or anxiety, while Cohort 2 evaluated the risk of subsequent depression or anxiety among patients with newly diagnosed IBS. Propensity score matching, multivariable Cox regression, and Fine–Gray competing risk models were applied. Results IBS was associated with increased risks of depression (adjusted hazard ratio [aHR] = 1.55) and anxiety (aHR = 1.68). Conversely, depression and anxiety were associated with higher risks of developing IBS (aHR = 1.45 and 1.51, respectively). Associations were stronger among females and younger adults aged 18–39 years. Sleep disorders (SDs) showed the strongest modifying effect in both directions (sub-distribution HR ≈ 1.60). Results were consistent across sensitivity analyses. Conclusions This nationwide longitudinal study demonstrates a robust bidirectional association between IBS and psychological distress, supporting integrated screening and multidisciplinary care approaches targeting gut–brain interactions.