Psychosomatic Medicine and Somatic Symptom Disorders Clinical Psychology, Psychotherapy, and Counseling

A Structural Model of Irritable Bowel Syndrome Symptom Severity Based on Perceived Stress: The Mediating Roles of Visceral Anxiety, Negative Symptom Expectations, and Interoceptive Dysfunction

https://doi.org/10.61838/ijbmc.v14i3.1514
Irritable Bowel Syndrome Negative Symptom Expectations Perceived Stress Visceral Anxiety

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In Press
Quantitative Study(ies)

Objective: This study examined a structural model of IBS symptom severity based on perceived stress, with visceral anxiety, negative symptom-related expectations, and disturbed interoceptive processing as parallel mediators.

Methods and Materials: This cross-sectional correlational study included 400 adults with Rome IV-confirmed IBS attending the Research Institute for Gastroenterology and Liver Diseases, Ayatollah Taleghani Hospital, Tehran, Iran, in 2025. Participants completed the Perceived Stress Scale, Visceral Sensitivity Index, Cognitive Scale for Functional Bowel Disorders, Body Perception Questionnaire–Short Form subdiaphragmatic reactivity subscale, and IBS Severity Scoring System. Structural equation modeling and bias-corrected bootstrapping with 5,000 resamples were used to evaluate direct and indirect associations.

Findings: The hypothesized model demonstrated good fit, χ²(10) = 22.48, CFI = .982, TLI = .956, RMSEA = .056, and SRMR = .032, and explained 57% of the variance in IBS symptom severity. Perceived stress significantly predicted visceral anxiety (β = .59), negative symptom expectations (β = .54), and interoceptive reactivity (β = .42). All three mediators were independently associated with greater IBS severity. Significant standardized indirect effects were observed through visceral anxiety (.20), negative symptom expectations (.15), and interoceptive reactivity (.07). The total indirect effect was .42, while the direct effect remained significant (β = .18).

Conclusion: Perceived stress was associated with IBS symptom severity both directly and indirectly through gastrointestinal-specific anxiety, negative symptom expectations, and disturbed interoceptive processing. Visceral anxiety represented the strongest indirect pathway. These findings support mechanism-focused psychological assessment and intervention in IBS.