Health Care Center for Pain Medicine and Mental Health Saarbrücken, D-66119, Saarbrücken, Germany; Department of Psychosomatic Medicine and Psychotherapy, Technische Universität München, D-81365, München, Germany. Electronic address: whaeuser@klinikum-saarbruecken.de. Epidemiology Group, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, UK; Aberdeen Centre for Arthritis and Musculoskeletal Health, University of Aberdeen, UK. Electronic address: gareth.jones@abdn.ac.uk.