Key words: irritable bowel syndrome, functional gastrointestinal disorders, abdominal pain, experience sampling method

"Measuring symptoms in Irritable Bowel Syndrome: Towards an Individualized and Daily Life approach"

Irritable bowel syndrome (IBS) is a common disorder of the brain-gut axis, characterized by abdominal pain and altered bowel habits. IBS diagnosis is symptom-based and therefore, accurate symptom registration is important for scientific research and clinical practice. In this thesis, the use of the most recent diagnostic criteria is evaluated and the (natural) course of symptoms over time is described. Subsequently, a new method for symptom registration in IBS, the experience sampling method (ESM), is developed and validated, and its applications are described.

In summary, this thesis describes the challenges of capturing the full picture of IBS symptoms, including heterogeneity between subjects, within-subject changes over time, and co-morbid psychological and environmental factors that may interfere with gastrointestinal symptoms. The research presented serves as a basis for the use of the ESM in IBS scientific research, and further implementation in clinical care will be future steps.

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