title: Which psychological factors exacerbate irritable bowel syndrome? Development of a comprehensive model.
abstract: OBJECTIVE
  There is evidence that psychological factors affect the onset, severity and duration of irritable bowel syndrome (IBS). However, it is not clear which psychological factors are the most important and how they interact. The aims of the current study are to identify the most important psychological factors predicting IBS symptom severity and to investigate how these psychological variables are related to each other.
  
  
  METHODS
  Study participants were 286 IBS patients who completed a battery of psychological questionnaires including neuroticism, abuse history, life events, anxiety, somatization and catastrophizing. IBS severity measured by the IBS Severity Scale was the dependent variable. Path analysis was performed to determine the associations among the psychological variables, and IBS severity.
  
  
  RESULTS
  Although the hypothesized model showed adequate fit, post hoc model modifications were performed to increase prediction. The final model was significant (Chi(2)=2.2; p=0.82; RMSEA<.05) predicting 36% of variance in IBS severity. Catastrophizing (standardized coefficient (β)=0.33; p<.001) and somatization (β=0.20; p<.001) were the only two psychological variables directly associated with IBS severity. Anxiety had an indirect effect on IBS symptoms through catastrophizing (β=0.80; p<.001); as well as somatization (β=0.37; p<.001). Anxiety, in turn, was predicted by neuroticism (β=0.66; p<.001) and stressful life events (β=0.31; p<.001).
  
  
  CONCLUSIONS
  While cause-and-effect cannot be determined from these cross-sectional data, the outcomes suggest that the most fruitful approach to curb negative effects of psychological factors on IBS is to reduce catastrophizing and somatization.
authors.affiliation: University of North Carolina, Center for Functional GI and Motility Disorders, Chapel Hill, NC 27599-7080, United States. tilburg@med.unc.edu
authors.forename: Miranda A L
authors.initials: MA
authors.lastname: van Tilburg
authors.forename: Olafur S
authors.initials: OS
authors.lastname: Palsson
authors.forename: William E
authors.initials: WE
authors.lastname: Whitehead
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001007:Anxiety / Q000523:psychology; D058443:Catastrophization / Q000150:complications / Q000523:psychology*; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000150:complications / Q000523:psychology*; D008016:Life Change Events; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D010551:Personality; D011788:Quality of Life / Q000523:psychology; D012720:Severity of Illness Index; D013001:Somatoform Disorders / Q000150:complications / Q000523:psychology*; D013315:Stress, Psychological / Q000150:complications / Q000523:psychology