1. Unger-Vetlesen Institute, Lovisenberg Diaconal Hospital , Oslo, Norway
2. Institute of Clinical Medicine, University of Oslo , Oslo, Norway
3. Department of Gastroenterology, Oslo University Hospital , Oslo, Norway
4. Norwegian National Advisory Unit on Concurrent Substance Abuse and Mental Health Disorders (Norwegian Centre of Dual Diagnosis), Innlandet Hospital Trust , Brumunddal, Norway
5. Norwegian Centre for Addiction Research, University of Oslo , Oslo, Norway