1. Department of General Practice, Institute of Health and Society, University of Oslo, Oslo, Norway
2. Norwegian Centre for Headache Research, Akershus University Hospital, Lørenskog, Norway
3. Department of Neurology, Akershus University Hospital, Lørenskog, Norway
4. Norwegian Competence Center for Sleep Disorders, Haukeland University Hospital, Bergen, Norway
5. Department of Psychosocial Science, University of Bergen, Bergen, Norway
6. Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway