1. Norwegian Centre for Addiction Research; University of Oslo; Oslo Norway
2. Department of Research and Development in Mental Health; Akershus University Hospital; Loerenskog Norway
3. Department of Addiction Medicine; Haukeland University Hospital; Bergen Norway
4. The University of Bergen; Bergen Norway
5. Department of Addiction Medicine; Oslo University Hospital; Oslo Norway
6. Vestfold Hospital Trust; Toensberg Norway
7. Institute of Clinical Medicine, Campus Ahus, University of Oslo; Blindern Norway
8. Health Services Research Unit; Akershus University Hospital; Loerenskog Norway