Abstract
Background: The association of IBS with psychiatric disorder remains uncertain. Relationships have been reported in some cross-sectional studies, however, these have failed to establish whether psychiatric disorder precedes a diagnosis of IBS or is a consequence of it. Few studies have examined whether psychiatric disorder is more important than personality factors in the etiology of IBS.
Method: The data were collected from a 1972 birth cohort (Dunedin, NZ) which has been followed through the first 26 years of life: 96% of the living cohort was assessed at the most recent follow-up (at age 26). IBS was diagnosed according to the Manning criteria, using symptom data collected at age 26. DSM-IIIR diagnostic information was collected at ages 18 and 21 years; a DSM diagnosis at both time points was used to define chronic psychiatric disorder (any), chronic depressive illness and chronic anxiety disorder. Personallity was assessed at age 18 years using the Multidimensional Personality Questionnaire (MPQ).
Results: Data was available for 869 subjects (49.6% female). Of these, 145 (16.7%) met the Manning criteria for IBS. This was significantly more common among females compared to males (19.5% vs 13.9%; p=0.03), but not among individuals with a history of psychiatric disorder. The lack of effect for psychiatric disorder was evident for any disorder (p=0.72), and for depressive illness (p=0.10) and anxiety disorder (p=0.53). Of the ten MPQ scales considered, only one emerged as a significant predictor of a diagnosis of IBS: mean scores on the Social Potency scale were significantly higher among subjects with IBS when compared to normal controls (mean: 42.2 vs 36.6; p=0.02). The difference remained significant after adjustment for subject gender (p=0.01).
Conclusions: In young adults, IBS is related to personality, but not to a history of psychiatric disorder. When compared to healthy controls, IBS patients were significantly more likely to report a socially "forceful" or dominant personality style.