Irritable bowel syndrome: a comparison of subtypes

Irritable bowel syndrome (IBS) is traditionally divided into subtypes depending on the bowel habit abnormality, but there is little clarity in the literature about whether these subtypes differ symptomatically or psychologically. Furthermore, there are conflicting reports on the relationship between symptom severity and psychological status. The aim of this study was to address these issues in a large cohort of patients defined by bowel habit.

One thousand IBS patients were divided into diarrhea (IBS-D), constipation (IBS-C), and mixed (IBS-M) bowel habit subtypes and completed a series of validated questionnaires capturing symptom severity, non-colonic symptomatology (somatization), quality of life, and anxiety or depression levels. Comparisons were made using SPSS version 20.

There were no significant differences between the three subtypes with respect to symptom severity, abdominal pain intensity, non-colonic symptomatology, quality of life, and anxiety or depression scores (all Ps > 0.05). In addition, there was only a small but statistically significant correlation between IBS symptom severity and both anxiety or depression, as well as quality of life (highest r = 0.34), while the relationship between somatization and disease severity was moderate (r = 0.42).

This study suggests that there are no differences in the symptom profiles and anxiety or depression scores between different subtypes of IBS. In addition, anxiety and depression do not appear to be strongly associated with symptom severity, although this does not exclude the possible interplay between these and other psychological drivers of severity, such as poor coping skills.