1. Chair of Complementary and Integrative Medicine, University of Duisburg-Essen, 45276 Essen, Germany
2. Institute for Medical Informatics, Biometry and Epidemiology, University Hospital of Essen, 45138 Essen, Germany
3. Department for Internal and Integrative Medicine, Kliniken Essen-Mitte, 45276 Essen, Germany
4. Department of Internal and Complementary Medicine, Immanuel Hospital Berlin, 14109 Berlin, Germany