1. University Medical Center Groningen, Department of Health Sciences, Section Health Psychology, University of Groningen, 9712 CP Groningen, The Netherlands
2. University Medical Center Groningen, Department of Gastroenterology and Hepatology, University of Groningen, 9712 CP Groningen, The Netherlands
3. University Medical Center Groningen, University of Groningen, 9712 CP Groningen, The Netherlands