Changes in illness-related cognitions rather than distress mediate improvements in irritable bowel syndrome (IBS) symptoms and disability following a brief cognitive behavioural therapy intervention
Introduction
Irritable bowel syndrome (IBS) is a prevalent chronic condition affecting around 10–20% of the population. It is associated with significant morbidity including impaired quality of life, depression and anxiety symptoms (Drossman et al., 1999, Levy et al., 2006). Whilst IBS is not associated with mortality (Owens, Nelson, & Talley, 1995) it significantly impacts upon direct and indirect health care costs (Akehurst et al., 2002).
Psychological therapies have shown to be efficacious in reducing IBS related symptoms, including gastrointestinal symptoms (GI), psychological distress and quality of life (Creed et al., 2003, Lackner et al., 2006, Lackner et al., 2004). Cognitive Behavioural Therapies (CBT) have shown to be particularly effective in improving IBS related outcomes (Blanchard et al., 2007, Greene and Blanchard, 1994, Kennedy et al., 2005, Moss-Morris et al., 2010, Payne and Blanchard, 1995, van Dulmen et al., 1996).
Quite how CBT leads to improved IBS outcomes remains less clear, with only a few studies examining mediators of change (Lackner et al., 2007, Reme et al., 2011). One argument is that CBT exerts treatment effects via improvements in psychological distress (Jones, Koloski, Boyce, & Talley, 2011). However, other evidence suggests that CBT has a direct effect on improved GI symptoms that in turn may lead to reductions in psychological distress (Lackner et al., 2007). Other studies of symptom-based disorders suggest that physical symptoms are more responsive to change following CBT than psychological distress (Kroenke & Swindle, 2000). A recent study found that a reduction in maladaptive behaviours and negative cognitions mediated the effect of CBT on improved IBS related outcomes i.e. decreased IBS symptom severity and disability (Reme et al., 2011). This study reported that mediation occurred first through changes in behaviour, then changes in cognition before impacting upon treatment outcome. However, this study used simultaneous assessments of process (mediator) and outcome variables, a method which is not ideal since to infer causality, mediators should precede in time the outcome variables (Kazdin, 2007).
The present paper explored potential cognitive and behavioural mediators of change following a relatively brief CBT based self-management intervention for IBS, using additional trial data from Moss-Morris et al. (2010). This short intervention was based on an empirical cognitive behavioural model of IBS (Spence & Moss-Morris, 2007) and demonstrated efficacy for improving IBS symptoms and social adjustment up to six months post treatment (Moss-Morris et al., 2010). The aims of the current study were to, 1) evaluate whether CBT altered cognitive, behavioural and emotional factors hypothesized to perpetuate IBS symptoms and disability 2) establish if proximal changes in these factors over the 2-month intervention period mediate the positive treatment effects of CBT 6 months later and 3) to ascertain if changes in cognition and behaviour, rather than mood, mediated improvement.
Section snippets
Patients
A full description of the original RCT, patient characteristics and study attrition rates are presented elsewhere (Moss-Morris et al., 2010). In the RCT, 64 IBS patients meeting Rome criteria (Thompson, 1999, Thompson et al., 1999) were randomized to receive either a CBT based self-management intervention plus treatment as usual (CBT, n = 31) or just treatment as usual (TAU, n = 33). In both groups 73% were female, with the majority having European ethnicity (CBT = 90%, TAU = 97%). The mean age
Does treatment change mood, cognitive and behavioural factors?
Table 1 displays mean change scores for each of the proposed cognitive and behavioural mediators for CBT and TAU groups. ANCOVA revealed that following intervention the CBT group reported less fear avoidance, catastrophizing and damaging beliefs compared to TAU patients. Furthermore CBT but not TAU patients had more positive illness perceptions and shifted from attributing symptoms predominantly to physical causes to viewing symptoms as related to both physical and psychological causes.
Discussion
This study explored potential cognitive and behavioural mediators of improved symptom severity and social adjustment following an RCT of a self-management CBT intervention in IBS patients. Specifically we examined whether changes in potential mediating factors over the two-month intervention period predicted outcomes six months later.
In accordance with hypotheses, our findings demonstrate significant change in a number of illness and symptom cognitions following CBT, but not TAU, that in turn
Conclusions
Changes in cognitive factors appear to mediate treatment effects of CBT upon IBS related outcomes. Altering illness perceptions seem to be a particularly important aspect of therapy in terms of achieving improvements to symptom severity and adjustment. These findings add to the current evidence base regarding the validity of a cognitive model of IBS rather than a model of somatic distress. This paves the way for more cognitive based interventions in this patient population in order to treat the
Conflict of interest
The authors declare no conflict of interest.
Acknowledgements
The original trial was funded by a University of Auckland staff fund (R. Moss-Morris).
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