Is the association between irritable bowel syndrome and abuse explained by neuroticism? A population based study

Background - In outpatients and the community, an association between abuse (particularly sexual abuse) and irritable bowel syndrome (IBS) has been observed, but whether there is a causal link continues to be disputed. Aims - To test the hypothesis that psychological factors explain the apparent association between abuse and IBS. Methods - A sample of residents of Penrith (a Sydney suburb sociodemographically similar to the Australian population) selected randomly from the electoral rolls (that by law include the entire population of age 18 years and above) was mailed a validated self report questionnaire. Measured were gastrointestinal (GI) symptoms including the Rome criteria for IBS, abuse (including the standardised Drossman questions), neuroticism (Eysenck Personality Questionnaire), and psychological morbidity (General Health Questionnaire). Results - The response rate was 64% (n = 730); 12% fulfilled the Rome criteria for IBS. Overall abuse in childhood (odds ratio (OR) = 2.02, 95% confidence interval (CI) 1.29 to 3.15) but not adulthood (OR = 1.39, 95% CI 0.88 to 2.19) was associated with IBS univariately. Neuroticism and psychological morbidity were also univariately associated with abuse in childhood, abuse in adulthood, and IBS, respectively. However, by logistic regressions abuse in childhood was not associated with lBS after controlling for age, gender, and psychological factors (OR = 1.34, 95% CI 0.83 to 2.17). The results were not altered by restricting the analyses to more severe forms of abuses and were not explained by interactions between abuse and psychological variables. Conclusion - There is an association between abuse and IBS in the community, but this may be explained in part by other psychological factors. Based on a path analysis, we postulate that abuse may induce the expression of neuroticism that in turn leads to IBS.