1 Medical Faculty Mannheim of Heidelberg University, Germany Department of Clinical Psychology and Psychotherapy, Marburg University, Marburg, Germany Wingate Institute of Neurogastroenterology, Centre of Digestive Diseases, Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, London, United Kingdom Academic Unit of Palliative Care, University of Leeds, Leeds, United Kingdom Department of Diagnostic Sciences, Rutgers School of Dental Medicine, Rutgers, Newark, NJ, USA St Vincent's Clinical School, UNSW Australia, Sydney, Australia Department of Neurology, Krankenhaus Lindenbrunn and Faculty of Medicine, University of Münster, Münster, Germany Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Denmark Department of Psychiatry, Columbia University, New York State Psychiatric Institute, New York, NY, USA Department of Medicine and Science of Aging, and Ce.S.I., G. D'Annunzio University Foundation, University of Chieti, Italy St Olavs Hospital, Trondheim University Hospital and European Palliative Care Research Centre (PRC), Department for Cancer Research and Molecular Medicine, Faculty of Medicine, NTNU, Norway Department of Clinical Neuroscience, Karolinska Institute Stockholm, Sweden Department of Anesthesiology and Acute Postoperative Pain Service, Saint Luc Hospital, Catholic University of Louvain, Brussels, Belgium University of Sydney Medical School, Australia Pain Clinic, Hotel Dieu Hospital, Paris Descartes University, INSERM U 987, Paris, France Departments of Anesthesiology and Pharmacology, Columbia University, New York, USA Pharmacology, Pharmacy and Anesthesiology Unit, School of Medicine and Pharmacology, University of Western Australia and Pain Medicine, Royal Perth Hospital, Perth, Australia Division of Population Health Sciences, University of Dundee, Scotland Section of Clinical Oral Physiology, School of Dentistry, Aarhus University, Denmark Department of Dental Medicine, Karolinska Institute, Huddinge, Sweden Research Group Health Psychology, University of Leuven, Leuven, Belgium Department of Clinical Psychological Science, Maastricht University, Maastricht, the Netherlands The Neurological Institute, Taipei Veterans General Hospital and Faculty of Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan.