Psychosocial Factors are Linked to Functional Gastrointestinal Disorders: A Population Based Nested Case-Control Study

G. Richard Locke, III, M.D.; Amy L. Weaver, M.S.; L. Joseph Melton III, M.D.; Nicholas J. Talley, M.D., Ph.D.

Disclosures

Am J Gastroenterol. 2004;99(2) 

In This Article

Abstract and Introduction

Background: It is widely accepted based on volunteer studies that levels of psychological distress are similar in those with functional gastrointestinal (GI) disorders and health in the community, while increased psychological distress in outpatients is largely explained by health-care seeking.
Aims: To determine if psychological distress, life event stress, or social support is associated with functional GI disorders in a population-based study.
Methods: A nested case-control study was performed by first mailing a self-report bowel disease questionnaire to a random sample of Olmsted County, Minnesota, aged 20-50 yr. All persons who reported symptoms of nonulcer dyspepsia (NUD) or irritable bowel syndrome (IBS) (cases), or an absence of GI symptoms (controls), were invited to complete a series of validated questionnaires designed to measure psychological distress, life event stress, social support, current symptoms, and physician visits.
Results: 103 subjects with functional GI disorders and 119 controls participated (85% of eligible). Functional GI disorders were more likely to be reported by those with higher scores on each of the nine SCL-90-R scales used to measure psychological distress (except phobic anxiety), and those with more negative and total life event stress. In a multiple logistic regression model (including age and gender), somatization, interpersonal sensitivity, and total life event stress were independently associated with functional GI disorders. Findings were similar when subjects with the IBS and NUD were analyzed separately compared to controls.
Conclusions: Contrary to current dogma, psychosocial factors were significantly associated with functional GI disorders in this community sample. This suggests that these factors may be involved in the etiopathogenesis rather than just driving health-care utilization.

Functional gastrointestinal (GI) disorders such as the irritable bowel syndrome (IBS) and nonulcer dyspepsia (NUD) are characterized by chronic symptoms referable to the gastrointestinal tract in the absence of any biochemical or structural explanation.[1,2] The cause of these disorders remains essentially unknown, but psychological factors have been implicated. For example, patients with NUD report more life stress and psychologic distress[3,4,5,6,7,8] than healthy controls in clinic-based studies. Similarly, patients with IBS who present to tertiary referral centers have a higher prevalence of psychologic distress, major depression, somatization, hypochondriasis, and anxiety than healthy controls.[9,10,11] By contrast, studies among volunteers have demonstrated no psychological differences between people with IBS who have not seen a physician compared to community-based healthy controls.[12,13,14] This has led to the conclusion that the association of psychological distress and psychiatric disorders with IBS is primarily related to health-care seeking behavior (i.e., confounding) rather than the underlying disease per se. However, volunteer samples are potentially prone to selection bias, and population-based studies that have carefully evaluated the influence of psychological factors on IBS are sparse.[15,16,17,18] Thus, whether IBS and psychological distress are causally linked, and are independent of health-care seeking, remains unclear.[19]

Stress may play a role in functional GI disorders but this is also controversial.[6,7,8,20] More severe life event stress has been found to be a very strong predictor of subsequent symptom severity in outpatients with IBS and NUD,[20] but no community studies have carefully evaluated whether stress is linked to disease or just to health-care seeking. Lack of social support could theoretically predispose a vulnerable person to experience worse disease under stress and hence seek more care,[21,22,23] but this has not been assessed in the population.

We utilized a population-based, case-control design to test the hypotheses that greater psychological distress, more life event stress and threatening experiences, and less social support are associated with having a functional GI disorder, or separately IBS or NUD.

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