Anxiety Moderates the Relationship Between Stress and Pain in IBS Patients: A Prospective Diary Study

Background/Objectives: Irritable bowel syndrome (IBS) is a common disorder of brain–gut interaction characterized by abdominal pain and altered bowel habits. While stress and anxiety are known to exacerbate IBS symptoms, less is understood about how these factors interact on a daily timescale. This study aimed to clarify the relationship between daily stress and abdominal pain in IBS and to examine whether trait anxiety moderates this association. Methods: Forty-nine IBS patients completed daily assessments of stress and abdominal pain over a 14-day period. Participants rated abdominal pain three times daily and reported daily stress levels across seven life domains each evening. Trait anxiety was assessed at baseline using the STAI-T. Results: Hierarchical linear modeling was used to analyze within-person and between-person effects. An increase in between-person stress was associated with increased probability of abdominal pain among individuals with low-to-moderate trait anxiety, while this was not observed in patients with high trait anxiety. Even though within-person (day-to-day) stress variations had an impact on pain probability, the effects of between-person variations were multiple times greater. Conclusions: These findings suggest that the interplay between stress and anxiety in IBS might not be uniform. High trait anxiety may, under certain conditions, attenuate rather than amplify the link between stress and pain, possibly pointing to a more dynamic relationship.