School of Psychiatry and Behavioural Science, University of Manchester
Department of Psychiatry, University of Sheffield
Centre for Health Economics, University of York
School of Psychiatry and Behavioural Science, University of Manchester
Institute of General Practice, Northern General Hospital, Sheffield
Section of Gastrointestinal Science, Hope Hospital, University of Manchester, Manchester, UK
North of England IBS Research Group
Correspondence: Professor Francis Creed, School of Psychiatry and Behavioural Science, Rawnsley Building, Oxford Road, Manchester M13 9WL, UK. Tel: +44 (0)161 276 5331/5397; fax: +44 (0)161 273 2135; e-mail: francis.creed{at}man.ac.uk
Declaration of interest F.H.C. has consultancy links with Eli Lilly and Lundbeck; S.P. has consultancy links with AstraZeneca and Eli Lilly.
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ABSTRACT |
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Aims To assess the contribution of psychiatric disorders to impaired outcome in severe irritable bowel syndrome.
Method Patients with severe irritable bowel syndrome entering a psychological treatment trial (n=257) were interviewed using the Schedules for Clinical Assessment in Neuropsychiatry. Outcomes were number of days of restricted activity, role limitation (physical) score of the Short Form Health Survey and costs.
Results At baseline, depressive disorder (29% of patients), panic (12%) and neurasthenia (35%) were associated with impairment; number of psychiatric disorders was associated in a dose-response fashion (P=0.005). At follow-up, depressive disorder and neurasthenia were associated with role limitation score. Improved depression was associated with improved role functioning.
Conclusions Depressive, panic and neurasthenic disorders contribute to poor outcomes in severe irritable bowel syndrome, and appropriate treatment should be available to these patients.
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INTRODUCTION |
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METHOD |
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All people attending the clinics with irritable bowel syndrome were screened and those who fulfilled the inclusion criteria were invited to enter the trial. These were patients 18-65 years old who fulfilled the Rome I criteria for this syndrome (Thompson et al, 1992), with symptoms for 6 months or more and a pain severity score of more than 59 on a 0 to 100 visual analogue scale, who had not responded to usual medical treatment including education, dietary advice, and antispasmodic and laxatives or antidiarrhoeal medication. We excluded patients who were unable to complete questionnaires in English, who had a psychotic disorder, severe personality disorder or active suicidal ideation, or had a contraindication either to psychotherapy or to taking an SSRI (e.g. taking medication that could interact with an SSRI, such as sumatriptan, warfarin and anticonvulsants).
Ethics committee approval was obtained for each hospital taking part in the study and all participants signed written consent forms to participate in the study. Before randomisation the trial participants underwent the following assessments.
Assessment of abdominal pain and bowel symptoms
The diagnosis of irritable bowel syndrome according to the Rome criteria
was made using the relevant questionnaire, which includes a measure of pain
severity, using a visual analogue scale
(Drossman et al,
1995). Since abdominal pain is the cardinal symptom of the
syndrome (Maxton et al,
1989; American Gastroenterology
Association, 2002), severity of pain was used as the prime measure
of severity of the syndrome. Patients also completed a daily diary recording
the severity of ten symptoms (nausea, abdominal pain, flatulence, bloating,
hard stool, loose stool, urgency, straining, incomplete evacuation and mucus),
using a seven-point Likert scale. This diary was kept for 14 days prior to
trial entry and follow-up, and the mean daily symptom score was used in the
analysis.
Assessment of psychiatric disorder
Psychiatric disorder at trial entry was diagnosed according to ICD-10
criteria (World Health Organization,
1992) using the Schedules for Clinical Assessment in
Neuropsychiatry (SCAN; World Health
Organization, 1994), administered by a trained psychiatrist. The
details of each psychiatric symptom are recorded directly on to a computerised
program that produces psychiatric diagnoses according to standardised research
criteria. Nine disorders are considered in this report (see Results). The SCAN
produces multiple psychiatric diagnoses and the number of psychiatric
diagnoses is also quoted in this report. The Hamilton Rating Scale for
Depression (HRSD; Hamilton,
1960) was used to measure severity of depression.
Outcomes
Impairment of daily activities
Impairment of daily activities was measured in two ways. First, each
participant noted the number of days over the previous month in which normal
activities were restricted because of the syndrome. Second, the role
limitation (physical) sub-scale of the 36-item Short Form Health Survey
(SF-36; Ware & Sherborne,
1992) was used. This scale closely captures the most common
concerns of patients with irritable bowel syndrome - impairment of work, home
life and social activities. It is the SF-36 sub-scale that shows least
correlation with neuroticism and with psychological distress
(Whitehead et al,
1996) and the greatest sensitivity to severity of irritable bowel
syndrome, most clearly distinguishing patients with the syndrome from normal
controls (Hahn et al,
1997).
Healthcare and other costs
All patients received healthcare from a single health provider, the UK
National Health Service (NHS), so utilisation data were taken directly from
the patient's hospital and primary care notes. Direct healthcare costs were
derived by applying an appropriate unit cost to each recorded contact or
episode of care. These included hospital in-patient days, out-patient,
day-patient and accident and emergency department attendances, and all primary
care contacts (medical consultations and home visits, practice nurse and
practice-based counsellors). Additional costs were derived from an interview
with the patient using the Client Service Receipt Inventory
(Beecham & Knapp, 1992); these included use of day centres, alternative therapies and prescribed
medications, and indirect costs such as travel costs and additional patient
expenditure as a result of the illness, non-prescription medication and any
additional expenditure relating to housework, childcare or personal care.
Indirect (loss of productivity) costs were measured by applying the patient's
daily wage to the number of days lost either through illness or clinic
attendance. The total of all healthcare, indirect and productivity costs is
quoted in the results.
Data analysis
In preliminary analyses we compared patients with and without each
psychiatric disorder (see Table
1) using one-way analysis of variance (ANOVA). Patients with and
patients without any psychiatric diagnosis, using the criterion of SCAN Index
of Definition (ID) level 5 or above, were compared using 2 and
t-tests (see Table 2).
In the main data analysis the predictor variables were psychiatric disorder
and number of psychiatric diagnoses. The outcome variables, recorded both at
trial entry and at follow-up, were number of days of restricted activity,
SF-36 role limitation (physical) sub-scale score, and total costs. Age,
gender, number of other medical conditions for which medication was being
taken and severity of abdominal pain (recorded at baseline) were treated as
possible confounders. All data were entered and analysed on the Statistical
Package for the Social Sciences, version 11.5. The first, cross-sectional
analysis compared the patients with and without each psychiatric diagnosis in
terms of impairment measured at baseline (i.e. at the time the diagnosis was
made) and with costs incurred over the previous year. These analyses used
analysis of covariance (ANCOVA) with the possible confounders (listed above)
as covariates.
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Multiple regression was used to identify the independent variables associated with number of days of restricted activity, SF-36 role limitation (physical) score and (log) costs. The variables entered into these regression analyses were: age, gender, marital status, years of education, number of other medical problems, abdominal pain severity (visual analogue scale), number of days with pain, and psychiatric disorder (depressive and panic disorders and neurasthenia). The expectation maximisation algorithm was used for missing data.
The prospective analyses assessed whether the psychiatric diagnosis recorded at trial entry was associated first, with the number of days of restricted activity and SF-36 role limitation (physical) score recorded at follow-up, and second, with costs incurred in the 12 months between the end of treatment and follow-up. These analyses used ANCOVA with treatment group (antidepressants, psychotherapy or treatment as usual) and baseline scores as covariates, in addition to the variables listed in the previous paragraph.
Patients with depressive or panic disorder were divided into two groups according to whether their HRSD score had dropped to 10 or below at 15 months' follow-up, indicating remission (Frank et al, 1991). The resulting groups of resolved and unresolved depression were compared using ANCOVA with the same covariates as before. To assess whether there was a significant treatment by diagnosis effect, an analysis was performed which used the change in SF-36 role limitation score between trial entry and follow-up as the outcome variable. The ANCOVA included as covariates age, gender, number of other medical conditions, pain severity, baseline SF-36 role limitation score and treatment group. The first analysis assessed the effect of depressive disorder, treatment group (psychotherapy, antidepressants and treatment as usual) and the interaction of depressive disorder and treatment group. The second analysis included neurasthenia instead of depressive disorder.
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RESULTS |
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Psychiatric disorders
Almost half of the participants (121; 47%) were classified by the SCAN
programme as reaching the threshold for psychiatric disorder (ID level 5 or
above). The numbers of patients assigned to each diagnosis is shown in
Table 1. The diagnoses not
shown were dysthymia 17 (7%), phobias 39 (15%), undifferentiated somatoform
disorder 24 (9%) and drug or alcohol problems 21 (8%). Many patients had more
than one disorder: for example, of the 74 patients with depressive disorder,
16 also had panic disorder, 6 had hypochondriasis and 41 had neurasthenia.
Associated features of psychiatric disorders
Patients with psychiatric disorder (ID level 5 or above) did not differ
significantly from the remainder with socio-demographic features or symptom
type, but they had more other medical conditions and more severe abdominal
pain (Table 2). Those with
neurasthenia were younger, and SF-36 role limitation scores were higher in
women. All subsequent analyses were therefore adjusted for age, gender, number
of other medical conditions and severity of abdominal pain.
Psychiatric disorders and outcome measures at baseline
At baseline, depressive disorders, panic disorders and neurasthenia were
associated with both restricted activity and impaired role functioning;
depressive and panic disorders were associated with increased total costs
(Table 3). No other psychiatric
diagnosis was associated significantly with these outcomes. Of the 70 people
unable to work owing to illness, 30 (43%) had depressive disorder, compared
with 44 out of 187 (24%) of those able to work (OR=2.4, 95% CI 1.4-4.4), and
17 (24%) had panic disorder, compared with 13 out of 187 (7%) of those able to
work (OR=4.3, 95% CI 2.0-9.4). No other psychiatric disorder was associated
with unemployment through ill health.
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At baseline the number of psychiatric disorders was associated with number of days of restricted activity, SF-36 role limitation (physical) score and total costs in a dose-response fashion (Figs 1, 2, 3).
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Does psychiatric disorder at baseline predict outcome 15 months later?
Of the three psychiatric diagnoses associated with impairment at baseline,
only one - neurasthenia - was significantly associated with number of days per
month of restricted activity at follow-up: 11.7 days (s.e.m.=1.1) compared
with 7.5 (s.e.m.=0.8) for the patients without neurasthenia (P=0.004,
adjusted for treatment group as well as age, gender, number of medical
conditions, severity of abdominal pain at baseline and baseline value of days
of restricted activity). Neurasthenia and depressive disorder were both
associated with SF-36 role limitation (physical) score at follow-up:
neurasthenia: 37.1 (s.e.m.=4.5) v. 53.5 (s.e.m.=3.2), adjusted
P=0.004; depressive disorder: 35.3 (s.e.m.=4.9) v. 53.1
(s.e.m.=3.1), adjusted P=0.003; (P adjusted for similar
covariates, except baseline value of SF-36 role limitation was used instead of
days of restricted activity). The number of psychiatric disorders at baseline
predicted SF-36 role limitation score at follow-up
(Fig. 2) but not days of
restricted activity or costs (Figs
1,
3).
Change over 15 months of the trial
Of the 82 patients with depressive and/or panic disorder at baseline, 35
had an HRSD score of 10 or less at follow-up. This resolved group had an
adjusted HRSD score at baseline of 14.9 (95% CI 13.1-16.6), compared with a
baseline adjusted HRSD score of 17.0 (95% CI 15.5-18.5) for the unresolved
group (n=47); P=0.052. At follow-up the HRSD score for the
resolved group had fallen by approximately 10 points to an adjusted mean of
5.0, whereas the adjusted mean score of the unresolved group remained the same
(Table 5). The resolved group
experienced significantly fewer days of restricted activity than the
unresolved group during the month prior to follow-up assessment. The SF-36
role limitation score showed significantly less impairment in the resolved
group than in the unresolved group but there was no difference in overall
costs (Table 5).
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Changes in SF-36 score with treatment
The results of the two-way ANCOVA assessing the effect of depressive
disorder and treatment group indicated that there was a significant effect of
depressive disorder (Fig. 4).
For the 64 patients with depression the adjusted mean change in the SF-36
physical role limitation sub-scale score was -1.6 (s.e.m.=4.9); the
corresponding score for the 155 patients without depression was 17.2
(s.e.m.=3.1); P=0.002. The difference between treatment groups was of
borderline significance: psychotherapy 10.4 (s.e.m.=5.1), paroxetine 14.8
(s.e.m.=4.6) and treatment as usual -1.79 (s.e.m.=5.0); P=0.049.
There was no significant treatment x depression interaction
(P=0.28).
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DISCUSSION |
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The psychiatric disorders we identified in our participants were mild in intensity compared with those usually treated by psychiatrists or included in trials of depressive disorder. However, the adverse effect on outcome is important. Impairment of health-related quality of life in irritable bowel syndrome has been reported by others as being comparable with that occurring in gastro-oesophageal reflux disease, diabetes and heart disease (Naliboff et al, 1998; Drossman et al, 2000; Gralnek et al, 2000; Luscombe, 2000; Lea & Whorwell, 2001; El-Serag et al, 2002), but only two of these six reports have acknowledged that this impairment could be attributed, in part, to co-existing psychiatric disorder (Naliboff et al, 1998; Drossman et al, 2000).
Our study draws attention to the component of impairment that is potentially treatable by psychological means. We found that patients with depressive or neurasthenic disorders who did not receive psychotherapy or paroxetine tended to show a worsening of their SF-36 role limitation scores. If psychiatric disorders are not recognised and treated in this population, people with severe irritable bowel syndrome may suffer unduly and miss time from their work or usual household activities. Since the syndrome was so long-standing it is likely that many patients had had untreated psychiatric disorders for months or even years.
Our sample was particularly impaired because of the way the participants were recruited. Even those without a coexisting psychiatric disorder had low SF-36 scores, reflecting severe abdominal pain and bowel disturbance (Hahn et al, 1997). For patients with psychiatric disorder the very low SF-36 scores were similar to those previously reported in studies of severe comorbid physical and psychiatric disorders (Ware et al, 1994; Creed et al, 2002). Like others, we have found that this combination of physical and psychiatric disorder leads to high costs because of time missed from work and expensive healthcare (Druss et al, 2000).
The strengths of the study are its large sample size, its representative nature (81% of eligible patients were recruited), the detailed measures and its prospective design. We were able to measure healthcare costs in an objective manner using NHS records, but we have quoted only total costs (i.e. healthcare and loss of productivity) for the sake of brevity. Our measures of impairment of daily living were self-reported, but great care was taken to record days of restricted activity accurately as part of the costing exercise. We have reported elsewhere that SF-36 scores are significantly associated with time off work, which provides some evidence of the validity of this self-report measure (Creed et al, 2003). The prospective design was limited by the fact that two-thirds of patients received either antidepressants or psychotherapy, but we were able to show no treatment by diagnosis interaction.
The adjustment for severity of abdominal pain was important because this was the principal predictor of impaired function and costs at baseline (see Table 4). It allowed us to identify the component of impairment that could be attributed to coexisting psychiatric disorders. We might have reduced the strength of the association, however, because there was a significant association between psychiatric disorder and abdominal pain severity score. Our results may provide a conservative estimate of the association between psychiatric disorder and outcome. A further theoretical consideration lies in the possibility that the main predictor of outcome is the total number of symptoms (physical and psychological) and that irritable bowel syndrome and depressive, panic and neurasthenic disorders might be seen as overlapping disorders. Although this is possible, the fact that severity of abdominal pain and psychiatric disorders contribute independently towards health-related quality of life argues for independent influences of these syndromes.
We chose to use the single SF-36 scale of physical limitation because of its lack of close correlation with neuroticism and its close correlation with patients' views of the disabling nature of severe irritable bowel syndrome. We found that it was the sub-scale (of eight) that most closely correlated with days of restricted activity at baseline and at follow-up (data not shown). The only scale that correlated more highly was the physical component summary score, but we could not use this score because it is a composite scale which includes a measure of pain, so that adjustment for severity of pain would have been unsatisfactory.
There were three main weaknesses of this study. First, this is a secondary analysis of a data-set that was collected for another purpose and patient numbers are not large enough to test adequately all the questions regarding healthcare and productivity costs. Second, although our sample was representative of patients with severe irritable bowel syndrome in gastroenterology clinics, the results cannot be generalised to all patients with this syndrome, most of whom have milder forms of the disorder. Third, because our patients were in a trial, two-thirds received an intervention, which has affected outcome; this is not a naturalistic study. Our study might have been underpowered to detect a true treatment by diagnosis interaction.
The diagnosis of neurasthenia is similar to that of chronic fatigue syndrome, and one other paper has reported that the presence of chronic fatigue in patients with irritable bowel syndrome is associated with impaired health-related quality of life and poor outcome (Simren et al, 2001). It is recognised that chronic fatigue syndrome, fibromyalgia and psychiatric disorders often occur together with irritable bowel syndrome (Whitehead et al, 2002); such comorbidity is associated with greater impairment than when the syndromes occur singly (Sperber et al, 2000). Neurasthenia is one of the most disabling conditions in population studies and the number of days of restricted activities increased with increasing number of comorbid conditions (Andrews et al, 1998).
The mechanisms by which depressive, panic and neurasthenic disorders lead to increased impairment and healthcare costs are not totally clear. Because we controlled for the effect of pain and other medical conditions, these cannot be explanations for high healthcare and other costs as suggested previously (Simon et al, 1995). It is likely that psychiatric disorders act in several ways: they may lead to worsening of pain and bowel dysfunction, they may exacerbate worry about illness and bodily symptoms (Gomborone et al, 1995) and they may reduce motivation to perform daily tasks.
The major implication of these results is that clinicians should consider whether psychiatric disorders are present in patients with severe irritable bowel syndrome, and if so, appropriate treatment should be offered. Recommendations for treatment of the severe syndrome suggest psychological or behavioural treatments, rather than medication directed towards relieving gut symptoms (American Gastroenterology Association, 2002). This has major implications for healthcare provision. Gastroenterologists or primary care physicians should be prepared to screen all such patients for psychiatric disorders and suitably trained health professionals need to be available for complex cases. The current referral pattern of highly selected patients within the traditional consultation-liaison model is unlikely to address adequately the unmet needs of these patients (Lloyd & Mayou, 2003). The professional background of the mental health professional is less important than readiness to see these patients, who appear to respond equally well to antidepressants prescribed by a gastroenterologist or general practitioner, or psychotherapy administered by a suitably trained therapist (Creed et al, 2003).
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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REFERENCES |
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Received for publication September 18, 2003. Revision received March 24, 2004. Accepted for publication September 17, 2004.
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