The prevalence of irritable bowel syndrome in outpatients with bulimia nervosa

Authors

  • Hannah DeJong BA,

    Corresponding author
    1. Section of Eating Disorders, Department of Psychological Medicine, Institute of Psychiatry, King's College London, United Kingdom
    • Section of Eating Disorders, Institute of Psychiatry, King's College London, United Kingdom
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  • Sarah Perkins Dclinpsy,

    1. Section of Eating Disorders, Department of Psychological Medicine, Institute of Psychiatry, King's College London, United Kingdom
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  • Miriam Grover MSc,

    1. Section of Eating Disorders, Department of Psychological Medicine, Institute of Psychiatry, King's College London, United Kingdom
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  • Ulrike Schmidt MD PhD

    1. Section of Eating Disorders, Department of Psychological Medicine, Institute of Psychiatry, King's College London, United Kingdom
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Abstract

Objective:

This study examined the prevalence of irritable bowel syndrome (IBS) in patients with bulimia nervosa (BN), and the relationship between these disorders.

Method:

Sixty-four participants with a diagnosis of BN or a related condition were recruited from an outpatient eating disorders service. Questionnaire and interview measures were used to assess bulimic symptoms and attitudes, IBS symptoms, anxiety and depression. Cases of IBS were identified using the Manning criteria.

Results:

There was a high prevalence of IBS in the patient group (68.8%), but IBS status was not predicted by any of the other variables measured. Patients who met criteria for IBS reported more frequent self-induced vomiting than those who did not (U = 256.0, p = 0.038).

Discussion:

There is evidence of an high incidence of IBS in outpatients with BN, but the relationship between these conditions remains unclear. Future research should consider possible common risk factors. © 2011 by Wiley Periodicals, Inc.

Introduction

There is a complex relationship between Eating Disorders (EDs) including BN, and Gastrointestinal (GI) symptoms. Before presenting to healthcare services with an ED, it is common for patients to seek treatment for GI symptoms.1 Conversely, once the ED is established, a range of GI symptoms (e.g., impaired gastric emptying, constipation, upper abdominal pain) can result from the behaviors associated with the disorder.2 There is also evidence that these symptoms may persist after recovery from an eating disorder, as indicated by a high prevalence of lifetime eating disorders (15.7%) in patients seeking treatment for Functional GastroIntestinal Disorders (FGIDs).3

One of the most frequently occurring forms of gastrointestinal disorder, and the diagnosis most commonly encountered by gastroenterologists,4 is Irritable Bowel Syndrome (IBS), which presents with abdominal pain, bloating, and disturbed defecation. IBS is more common in women than men, with one British study finding diagnosable IBS in 13% of women and 5% of men in a community sample.5 IBS can be defined using the Manning criteria—a list of symptoms that are found more commonly in patients with IBS than in patients with other diagnosable GI conditions.6 These symptoms include: abdominal pain, pain relief with bowel action, passage of mucous, and feeling of incomplete evacuation.

A few studies have demonstrated an elevated incidence of IBS and other FGIDs in ED groups. Perkins et al.7 recruited 234 participants with current or past eating disorder through a volunteer register and found that 64% of this group met Manning criteria for IBS. Meeting these criteria was associated with current Eating Disorder Examination Questionnaire (EDE-Q)8 scores—i.e., levels of dietary restriction, shape concern, weight concern, and eating concern. The number of IBS symptoms experienced was also correlated with EDE-Q scores and with frequency of inappropriate laxative use.

Similarly, Boyd et al.9 found that 98% of a sample of 101 patients admitted to an eating disorder unit met criteria for at least one FGID. The occurrence of FGIDs was similar across the ED diagnoses (i.e., AN, BN, and EDNOS). The most prevalent GI condition was IBS, with 52% of the patients studied meeting criteria. Somatization and state anxiety were predictors of IBS status.

This study was designed to extend previous findings regarding the relationship between IBS and EDs into a larger sample of patients with BN, and into a different setting—an outpatient eating disorders service. Outpatient care is the recommended treatment setting in the majority of cases of ED10 and so findings in this treatment setting are likely to generalize well and have broad-ranging implications for ED services. We hypothesized that there would be an elevated incidence of IBS in this group and that meeting criteria for IBS would be partly predicted by current ED symptoms.

Method

Participants

Participants were recruited from consecutive referrals to the Adult Eating Disorders Outpatients Service in the South London and Maudsley NHS Foundation Trust. Individuals who met DSM-IV11 diagnostic criteria for bulimia nervosa or for ED not-otherwise-specified bulimic type (EDNOS-BN), and who had engaged in key bulimic behaviors at least once per week over the preceding three months, were eligible to take part. Exclusion criteria for the study were insufficient English/literacy skills to complete research assessments, severe learning disability, anorexia nervosa, severe depression, acute suicidality, and alcohol/substance dependence. Individuals taking antidepressant medication were included, providing that they had been on a stable dose for a minimum of four weeks. All individuals gave written informed consent to participating in the trial, and the study was approved by the joint research ethics committee of the Institute of Psychiatry and the South London and Maudsley NHS Foundation Trust.

Measures

Participants were recruited as part of a larger treatment study.12 Diagnosis and duration of illness were determined in a clinical interview, and Body Mass Index (BMI) was calculated from measures of current height and weight (kg/m2).

Eating Disorders Examination

The EDE13, 14 was used to assess ED pathology. It is a semistructured interview that generates frequencies of key eating disorder symptoms (e.g., binging, self-induced vomiting, laxative use) and also four attitudinal subscale scores: dietary restraint, eating concern, shape concern, and weight concern. This is a widely used and detailed measure with good discriminant validity and satisfactory internal consistency.14

Hospital Anxiety and Depression Scale

The hospital anxiety and depression scale (HADS)15 was used to assess levels of comorbid anxiety and depression in the study participants. It generates anxiety and depression subscale scores, with a maximum score of 21 for each subscale. This questionnaire been shown to give clinically meaningful results when used as a psychological screening tool.16

Irritable Bowel Syndrome Questionnaire

The presence of IBS was assessed using a questionnaire designed for a previous study of IBS in eating disorders.7 It included questions on: symptoms of IBS based on the Manning criteria6; formal diagnosis of IBS; treatment for IBS. Participants were classified as meeting Manning criteria if they reported experiencing abdominal pain on more than six separate days in the past year, and at least two other relevant symptoms.

Analysis

Data were analyzed using SPSS for Windows, Version 15. The data did not meet parametric assumptions and so appropriate nonparametric tests were used throughout the analysis. Mann Whitney U tests were used to assess group differences. Spearman's correlations were performed to measure the relationship between IBS symptoms and clinical variables. Logistic regression was used to determine whether any of the clinical variables were associated with meeting the Manning criteria. A significance level of α = 0.05 was used for all tests.

Results

Sixty females and four male respondents completed the Manning questionnaire regarding IBS symptoms. The majority of the patients had a diagnosis of BN (N = 51), with the remainder having a diagnosis of EDNOS-BN (N = 12). In one case, diagnosis was not reported. The mean BMI was 23.38 (SD = 4.65), with a mean duration of illness of 8.92 years (SD = 7.61). Patients had a mean HADS anxiety score of 11.75 (SD = 1.81) and depression of 11.32 (SD = 2.01). Symptom frequencies and EDE scores are shown in Table1.

Table 1. Demographic and clinical measures
 MeasureMean (SD)
  1. EDE, eating disorders examination.

Average symptom frequency over past 3 monthsBinging (episodes per week)6.65 (10.44)
Self-induced vomiting (episodes per week)7.82 (11.10)
Laxative use (episodes per week).98 (2.60)
Food restriction (days per week)2.75 (3.28)
Excessive exercise (days per week).94 (2.05)
EDE scoresDietary restriction score3.42 (1.23)
Eating concern score2.72 (1.35)
Shape concern score4.10 (1.34)
Weight concern score3.40 (1.39)
Global score3.40 (1.09)

Forty-four patients (68.8%) met Manning criteria for IBS, 18 participants (28.1%) did not meet criteria and 2 participants (3.1%) did not provide sufficient information to establish this. Formal diagnosis of IBS was reported by 8 participants (12.5%), 51 patients (79.7%) reported no diagnosis and 5 participants (7.8%) did not answer this question. Seven participants (10.9%) reported receiving treatment for their GI symptoms, 44 participants (68.8%) reported no treatment, and the remaining 13 participants (20.3%) did not answer this question.

Those who met Manning criteria for IBS did not differ significantly from those who did not on any clinical variable except frequency of self-induced vomiting (U = 256.0, p = 0.038). This was higher for participants who met IBS criteria (M = 9.87, SD = 12.69) than for those who did not (M = 3.69, SD = 4.11). There were no significant correlations between the number of IBS symptoms reported and any other variable. Logistic regression was performed with duration of ED, current BMI, ED symptom frequency, EDE scores, and HADS scores all entered separately. None of these variables significantly predicted IBS status.

Discussion

The results of this study show that there is a high incidence of IBS in a group of outpatients diagnosed with BN or EDNOS-BN—with a large majority meeting the Manning criteria. As in previous studies, the rates of formal diagnosis and treatment of IBS were far lower than prevalence rates based on symptom criteria. Contrary to our predictions and the findings of Perkins et al.,7 the presence of IBS does not seem to be closely related to current eating disorder thoughts and attitudes, as measured by the EDE. Nor is it related to duration of ED, current anxiety and depression, or current frequency of eating disorder symptoms. Individuals who met Manning criteria for IBS reported more self-induced vomiting than the group who did not meet criteria, but this was not a significant predictor of IBS status.

Limitations

The study is limited by the sample used in several respects. First, it was relatively small, especially given how few participants did not meet criteria for IBS. This may have limited the ability to detect differences between groups, or to detect correlations between IBS status and other variables. Second, it is not clear to what extent this sample is representative of people with BN in the general population, many of whom are never referred to specialist ED services.17 The degree to which these results can be generalized may therefore be limited. Third, there was no healthy comparison group in this study and so it is not possible to determine the extent to which IBS prevalence in patients with BN differs from the prevalence found in healthy controls. The lack of a comparison group also limited our ability to assess possible risk factors for these disorders, particularly any common factors that contribute to risk for both conditions.

The use of the Manning criteria is also a limitation of the present study. These were used because the simple wording of the criteria lends itself to self-report of symptoms. However, they have now been largely superseded by the Rome II and Rome III criteria,18, 19 which provide an assessment of FGIDs that is more consistent with current research into these conditions. The study also focused on current psychopathology and eating behaviors, with no measure taken of lifetime psychopathology or change in ED symptoms over time. Finally, the study was limited by the failure to screen for organic GI disorder which, although quite rare in patients with EDs,20–27 could falsely inflate estimates of IBS incidence.

In summary, it seems that there is a high incidence of IBS in outpatients diagnosed with BN, coupled with a lack of recognition and treatment of this syndrome. The degree to which incidence of IBS is elevated in this group is not clear, due to the lack of a suitable comparison group. Future work that addresses this limitation may also allow researchers to address the possibility that there are common risk factors underlying both disorders.

The views expressed in this publication are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.

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