Background: Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterised by abdominal pain and altered bowel movements. Cognitive behavioural therapy (CBT) has been shown to be effective in reducing symptom severity in IBS and enhancing quality of life/functioning. The present study sought to identify how CBT achieves change in these outcomes.
Method: Secondary analysis was conducted on 149 patients with irritable bowel syndrome who had been randomised to cognitive behavioural therapy plus an antispasmodic medication or antispasmodic alone. Single and sequential mediation was modelled using structural equation modelling. Gastrointestinal (GI) related avoidance behaviour, safety behaviour, cognitions and general anxiety were included as mediators.
Results: GI safety behaviours, cognitions and general anxiety mediated treatment effect on the outcomes of symptom severity and work and social adjustment. Avoidance behaviour was not a significant mediator for either outcome. Sequential mediation models indicated that unhelpful GI related cognitions reduced before anxiety did, and this sequential path (R➔GI related cognitions➔anxiety➔outcome) was significant for both symptom severity (b = -0.22, CI [-0.40 to -0.90], p = .005) and work and social adjustment (b = -0.26, CI [-0.44 to -0.11], p = .003) where 'R' is randomisation. Reduction in GI safety behaviours also preceded reduction in anxiety. This sequence (R ➔GI safety behaviours➔anxiety➔outcome) was significant for both symptom severity (b = -0.11, CI [-0.24 to -0.01], p = .049) and work and social adjustment (b = -0.12, CI [-0.23 to -0.03], p = .03).
Conclusion: Results suggest that it is important for psychological treatments to target IBS specific factors for change.
Keywords: Anxiety; Cognitive behaviour therapy; Illness related cognitions; Irritable bowel syndrome; Safety behaviours; Treatment mechanisms.
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