ABSTRACT
Introduction: The brain-gut axis may influence disease outcomes in inflammatory bowel disease (IBD). Evidence supporting brain-gut axis activity would highlight a
need for novel management strategies targeting this pathophysiological mechanism in IBD. The aim of this thesis was to examine these issues directly.
Methods: In simultaneous cross-sectional studies, the relationship between symptom-reporting, psychological co-morbidity, and disease activity, and the prevalence of
irritable bowel syndrome (IBS)-type symptoms, as well as their association with impaired mood and quality of life, was assessed. In longitudinal follow-up, the temporal
relationship between disease activity and psychological co-morbidity was examined to assess for the presence of brain-gut axis activity. The relationship between the reporting of IBS-type symptoms and the natural history of IBD was also assessed. A systematic review and meta-analysis of randomised controlled trials was conducted to investigate the efficacy of psychological therapies in IBD.
Results: The correlation between symptom-reporting and mucosal inflammation was poor. Symptom-reporting, but not mucosal inflammation, was associated with psychological co-morbidity. Baseline disease activity was associated with new-onset anxiety (odds ratio = 5.17; 95% confidence interval (CI) 1.35-19.8), and baseline anxiety was associated with new-onset disease flare (hazard ratio = 2.08; 95% CI 1.31-3.30), suggesting possible bi-directional brain-gut axis activity in IBD. IBS-type
symptom-reporting was associated with psychological co-morbidity and poor quality of life, but reporting these symptoms was not associated with adverse longitudinal disease activity outcomes. Psychological therapies were associated with short-term beneficial effects on depression and quality of life, but had no effect on disease activity.
Conclusions: Bi-directional brain-gut axis activity may influence the natural history of disease activity, and psychological wellbeing, in IBD. Patients reporting IBS-type symptoms exhibit psychological co-morbidity and reduced quality of life. Evidence supporting the use of psychological therapies in IBD is poor, but trials of these treatments in patients at risk of mood disorders may still prove beneficial.
