[1] Univ Tromso, Dept Pediat, Univ Hosp Northern Norway, Tromso, Norway
[2] Univ Tromso, Dept Clin Med, Tromso, Norway
[3] Univ Oslo, Oslo Univ Hosp, Dept Pain Management & Res, Oslo, Norway
[4] Univ Calif Los Angeles, Div Digest Dis, Oppenheimer Family Ctr Neurobiol Stress, Los Angeles, CA USA
[5] Univ Calif Los Angeles, David Geffen Sch Med, Dept Med & Psychiat & Biobehav Sci, Los Angeles, CA 90095 USA
[6] Norwegian Inst Publ Hlth, Div Mental Hlth, Oslo, Norway