Functional gastrointestinal disorders: psychological characteristics

Despite the prevalence and disease burden of Functional Gastrointestinal Disorders (FGIDs), there are still several notable lacunae in the FGID research in terms of clearly classifying them by using a symptom-based approach, and the current psychological models of FGIDs. This thesis compared the patterns of psychological factors between two FGIDs. Additionally, an integrated psychological model of FGIDs was proposed and aspects of it were tested. Specifically, inter-relationships between FGID-specific psychological factors and a potential protective factor were tested. A series of analytical techniques were used. This thesis is presented in the form of three manuscript style chapters, preceded by a general introduction and followed with a general discussion. The first paper compared the patterns of psychological factors in two FGIDs (Irritable Bowel Syndrome and Functional Constipation), with the intention of expanding scientific knowledge about Functional Constipation, which has received little study. The second paper examined the inter-relationships between FGID-related illness representations, visceral sensitivity and mindfulness skills, and their influence on FGID symptoms and reported symptom severity. The third paper used a case series to examine the dynamic relationships between irritable bowel syndrome symptoms, distress, visceral sensitivity, and negative emotions as a result of an eight-week mindfulness skills training program. This last paper also compared the relative influence of visceral sensitivity versus generic negative emotions on FGID-related distress to ascertain the importance of visceral sensitivity in FGIDs. The findings from this thesis contribute to the field of FGID research by expanding our understanding of Functional Constipation, which has implications for the psychological treatment available for it. The results in this thesis also validate aspects of an integrated psychological model of FGIDs by increasing our understanding of the psychological factors specific to FGIDs, as well as considering the role of protective factors in FGIDs, which were hitherto unstudied.