1. Centre for Musculoskeletal Research, Department of Occupational Health Sciences and Psychology, Faculty of Health and Occupational Studies, University of Gävle, SE-801 76 Gävle, Sweden
2. Department of Public Health and Caring Sciences—Health Services Research, Uppsala University, SE-751 22 Uppsala, Sweden
3. Centre for Clinical Research, Region Västmanland—Uppsala University, Hospital of Västmanland, SE-721 89 Vasteras, Sweden
4. Department of Social Work and Criminology, Faculty of Health and Occupational Studies, University of Gävle, SE-801 76 Gävle, Sweden