Gastroenterology

Gastroenterology

Volume 122, Issue 4, April 2002, Pages 1140-1156
Gastroenterology

Special Reports and Reviews
Systematic review of the comorbidity of irritable bowel syndrome with other disorders: What are the causes and implications?,☆☆

https://doi.org/10.1053/gast.2002.32392Get rights and content

Abstract

Background & Aims: Comorbid or extraintestinal symptoms occur frequently with irritable bowel syndrome and account for up to three fourths of excess health care visits. This challenges the assumption that irritable bowel is a distinct disorder. The aims of this study were to (1) assess comorbidity in 3 areas: gastrointestinal disorders, psychiatric disorders, and nongastrointestinal somatic disorders; and (2) evaluate explanatory hypotheses. Methods: The scientific literature since 1966 in all languages cited in Medline was systematically reviewed. Results: Comorbidity with other functional gastrointestinal disorders is high and may be caused by shared pathophysiological mechanisms such as visceral hypersensitivity. Psychiatric disorders, especially major depression, anxiety, and somatoform disorders, occur in up to 94%. The nongastrointestinal nonpsychiatric disorders with the best-documented association are fibromyalgia (median of 49% have IBS), chronic fatigue syndrome (51%), temporomandibular joint disorder (64%), and chronic pelvic pain (50%). Conclusions: Multivariate statistical analyses suggest that these are distinct disorders and not manifestations of a common somatization disorder, but their strong comorbidity suggests a common feature important to their expression, which is most likely psychological. Some models explain the comorbidity of irritable bowel with other disorders by suggesting that each disorder is the manifestation of varying combinations of interacting physiological and psychological factors. An alternative hypothesis is that the irritable bowel diagnosis is applied to a heterogeneous group of patients, some of whom have a predominantly psychological etiology, whereas others have a predominantly biological etiology, and that the presence of multiple comorbid disorders is a marker for psychological influences on etiology.

GASTROENTEROLOGY 2002;122:1140-1156

Section snippets

Methodologic considerations

We searched the world medical literature indexed in Medline from 1966 to the present for the following terms: irritable bowel syndrome, IBS, functional bowel, and colonic disorders–functional, in conjunction with the terms comorbidity, comorbid disorder, psychiatric illness, psychiatric disorder, mental disorder, somatoform disorder, anxiety, anxiety disorder, depression, depressive disorder, panic, panic disorder, somatization, fibromyalgia, chronic fatigue syndrome, headache,

Do the comorbid disorders share pathophysiologic mechanisms with irritable bowel syndrome?

The 4 nongastrointestinal conditions just described that are strongly associated with IBS share some clinical features: They are all substantially more common in women, may be triggered or exacerbated by stress, and are associated with fatigue, sleep difficulties, anxiety, and depression. Furthermore, these 4 disorders all have a high degree of overlap with each other.30, 52 It would seem likely that disorders with so many similarities and excess overlap would share a common etiology; however,

Overlap with other functional gastrointestinal disorders

The comorbidity of IBS with other functional gastrointestinal disorders is even more striking than its overlap with nongastrointestinal somatic conditions; compare Table 3 with Table 1.

. Comorbidity of IBS with other gastrointestinal disorders

StudyMethodsSubjectsFindingsIBS Criteria and Comments
Kennedy et al. 199851Community survey3169 respondents including 546 with IBS, 442 with BHR, and 539 with GERD46.5% of IBS pts had GERD, and 47% of GERD pts had IBS (reported OR for the association: 2.72).

Is IBS a distinct entity or part of a global disorder?

This important question has been addressed by 3 types of studies: measurement of somatization, factor analysis, and multivariate statistical analysis.

Diagnostic ambiguity

All of the disorders that are comorbid with IBS are characterized by vague, sometimes overlapping symptoms,154 and Mayer et al.15 suggested that there is a physiologic basis for this vagueness: visceral afferents converge with somatic afferents on the same dorsal horn cells in the spinal cord, and the spinal segments to which visceral afferents project are overlapping. Wessely et al.155 further suggested that classification of these somatic symptoms into discrete diagnoses may be an artifact of

Study limitations

The studies reviewed here have a number of limitations, including the following:

  • Few of them are based on representative samples; most come from subspecialty clinics, which are affected by patient self-selection for treatment and other forms of ascertainment bias.

  • The case definitions for IBS and the other disorders of interest vary greatly across studies, and also have changed over time.

  • Many of the studies involve very small samples.

  • The criteria for diagnosis vary from patient self-report on

Comorbid disorders

Future work should assess large samples from either the general population or general medical patients, such as primary care patients; measure in the same samples all the commonly known comorbid conditions; and use well-defined clinical criteria for each of the disorders assessed.

Dual-etiology hypothesis

This hypothesis has implications for the kinds of experiments investigators might want to conduct on the pathophysiology and treatment of IBS. It suggests that it may be more productive to look for subgroups of

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    Address requests for reprints to: William E. Whitehead, Ph.D., Division of Digestive Diseases, CB#7080, University of North Carolina, Chapel Hill, North Carolina 27599. e-mail: [email protected].

    ☆☆

    Supported by NIDDKD (RO1 DK31369).

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