The central role of gastrointestinal-specific anxiety in irritable bowel syndrome: further validation of the visceral sensitivity index.

OBJECTIVES: The Visceral Sensitivity Index (VSI) was developed as the first instrument to assess gastrointestinal-specific anxiety, the cognitive, affective, and behavioral response to fear of gastrointestinal sensations, symptoms, and the context in which these visceral sensations and symptoms occur. The purpose of the current study was to a) replicate the previously reported psychometric properties of the VSI, b) assess the known-groups and concurrent validity of the instrument, and c) test conceptual hypotheses regarding gastrointestinal-specific anxiety in comparison to other general measures of psychological distress as a crucial mechanism (mediator/moderator) underlying irritable bowel syndrome diagnosis and its symptoms.
METHODS: Two undergraduate student samples (n > 500) were administered the VSI along with measures assessing presence of lower gastrointestinal symptoms, nongastrointestinal pain, health-service utilization, anxiety, depression, vitality, neuroticism, and anxiety sensitivity. Path analyses tested the hypothesis that gastrointestinal-specific anxiety mediates the relationship between affective variables and irritable bowel syndrome diagnosis and symptoms. A 'known-groups' validity approach elucidated the relevance of gastrointestinal-specific anxiety across a spectrum of irritable bowel syndrome patients.
RESULTS: Good concurrent, divergent and discriminant validity was demonstrated. Logistic regression revealed that gastrointestinal-specific anxiety is the key explanatory variable of irritable bowel syndrome diagnostic status. Path analysis demonstrated that gastrointestinal-specific anxiety mediates the relationship between general psychological distress measures and gastrointestinal symptom severity. The VSI was related to gastrointestinal, but not nongastrointestinal, symptom severity.
CONCLUSIONS: Overall, the VSI demonstrated excellent psychometric properties providing further support for its use in mechanistic studies of the role of anxiety in irritable bowel syndrome presentation.