[1] Haukeland Hosp, Dept Addict Med, Bergen Addict Res, Bergen, Norway
[2] Univ Bergen, Dept Global Publ Hlth & Primary Care, Post Box 7804, N-5020 Bergen, Norway
[3] Haukeland Hosp, Norwegian Res Ctr Agonist Treatment Subst Use Diso, Dept Addict Med, Bergen, Norway
[4] Stavanger Univ Hosp, Dept Resp Med, Stavanger, Norway
[5] Univ Bergen, Dept Clin Sci, Bergen, Norway
[6] Haukeland Hosp, Div Psychiat, Bergen, Norway
[7] Stavanger Univ Hosp, Ctr Alcohol & Drug Res, Stavanger, Norway
[8] Oral Hlth Ctr Expertise Rogaland, Stavanger, Norway
[9] Univ Stavanger, Dept Publ Hlth, Stavanger, Norway