Zsa Zsa Weerts

Chapter 10 246 pharmacological treatment and our findings of chapter 3 and 8 , it can be argued that future models of care and novel treatment strategies should preferably integrate the management of psychological comorbidities. A multidisciplinary and multidimensional approach likely leads to better treatment outcomes than standard care given by GPs and gastroenterologists. Treatment guidelines are indeed increasingly incorporating the promising biopsychosocial model of care, which simultaneously addresses both mood disorders and GI symptoms in patients with IBS. 31 The efficacy of psychological therapies alone, e.g. cognitive behavioral therapy 32,33 and hypnotherapy 34 has also been demonstrated in high quality studies. Nevertheless, therapist-led interventions are generally time consuming, relatively costly and the availability may be limited in some geographical areas due to a limited number of trained therapists. Psychological treatments that require less resources may increase cost-effectiveness, patient- satisfaction, and availability. Such treatments include 1) group hypnotherapy that has been shown to be non-inferior to individual hypnotherapy 35 ; 2) internet-delivered exposure-based cognitive behavioral therapy (CBT) that has been shown to reduce IBS symptoms 36 ; and 3) a primarily home-based CBT that has been shown to be at least as effective as standard CBT. 32 In that light, our group recently started a study to explore whether online hypnotherapy is non-inferior compared to individual face-to-face hypnotherapy in treatment of IBS symptoms (NCT03899779). It is hypothesized that such approaches can decrease treatment-associated costs, while simultaneously increasing general well-being and quality of life in patients with IBS. General conclusions This thesis has assessed the redefinition of diagnostic criteria and how this impacts the clinical diagnostic process in IBS. The potential effect on study populations in research has been described. Furthermore, this thesis has given an overview of current knowledge on TRP channels in IBS and provided the first in vivo data on the TRPM8 channel in IBS. Study findings described in this thesis are key in paving the way to develop novel TRP targeted therapies for IBS. At the center of this thesis is the PERSUADE study, the largest RCT with peppermint oil in IBS to date. This trial not only contributed to knowledge on peppermint oil, but also assessed efficacy using both strict endpoints according to regulatory guidelines and other clinically relevant but less robust endpoints. Findings in this thesis showed that peppermint oil is not only moderately effective, but also appears to be cost-effective. Trial data were collected using a digital data-collection method which is detailed further in this thesis and led to excellent adherence.