1. International Research Institute of Stavanger (IRIS); Box 8046 Stavanger Norway 4068
2. Bergen University College; Faculty of Health and Social Sciences; Haugeveien 28 Bergen Norway 5005
3. Oslo University Hospital Ullevål; Physical Medicine and Rehabilitation; Kirkevn 166 Oslo Oslo Norway 0407
4. Karolinska Institutet; Department of Clinical Neuroscience and Division of Insurance Medicine; Berzelius väg 3 Stockholm Sweden 171 77
5. Nordic School of Public Health; Gothenburg Sweden SE-40242