1. Faculty of Medicine and Health Technology , Tampere University , Tampere , Finland
2. Department of Anesthesiology, Intensive Care and Pain Medicine , University of Helsinki and Helsinki University Hospital , Haartmaninkatu 8 , 00290 Helsinki , Finland
3. Folkhälsan Research Center , Helsinki , Finland
4. Primary Health Care Unit, Kuopio University Hospital , Kuopio , Finland
5. Ilmarinen Mutual Pension Insurance Company , Helsinki , Finland
6. Department of Neurosurgery , Helsinki University Hospital , Helsinki , Finland
7. Department of Pediatrics , Päijät-Häme Central Hospital , Lahti , Finland
8. Department of Psychiatry , Päijät-Häme Central Hospital , Lahti , Finland
9. Department of Rheumatology , Päijät-Häme Central Hospital , Lahti , Finland