1 Centre for Epidemic Interventions Research, Norwegian Institute of Public Health, 0213 Oslo, Norway; Department of General Practice, Institute of Health and Society, University of Oslo, Oslo, Norway. Electronic address: signe.flottorp@fhi.no.
2 Division of Health Services, Norwegian Institute of Public Health, 0213 Oslo, Norway.
3 Department of Functional Disorders, Aarhus University Hospital, Aarhus, Denmark; Institute of Clinical Medicine, University of Aarhus, Aarhus, Denmark.
4 Department of Medical Psychology, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam Public Health Research Institute, Amsterdam, Netherlands.
5 Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Department of Paediatrics and Adolescent Medicine, Akershus University Hospital, Lørenskog, Norway.