1. Institute for Complementary and Integrative Medicine, University Hospital Zurich and University Zurich, Zurich, Switzerland.
2. Faculty of Health Sciences, Universidad Francisco de Vitoria (UFV), Madrid, Spain.
3. Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Unidad de bioestadística clínica, Hospital Universitario Ramón y Cajal, Madrid, Spain.
4. The Biomedical Research Center Network for Epidemiology and Public Health (CIBERESP), Madrid, Spain.
5. Institute for Social Medicine, Epidemiology and Health Economics, Charité–Universitätsmedizin Berlin, Berlin, Germany.
6. Center for Integrative Medicine, University of Maryland School of Medicine, Baltimore, MD, USA.