1. Department of Medical Psychology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;
2. Center of Health Care Research, University Medical Center Hamburg-Eppendorf, Hamburg, Germany;
3. Department of Medical Psychology and Medical Sociology, University Medical Center Leipzig, Leipzig, Germany;
4. Department of Psychosomatic Medicine and Psychotherapy, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany;
5. Department of Medical Psychology and Psychotherapy, Medical Sociology and Rehabilitation Sciences, and Comprehensive Cancer Center Mainfranken, University of Würzburg, Würzburg, Germany;
6. Professor for Self-Help Research, Comprehensive Cancer Center, University of Freiburg, Freiburg, Germany;
7. Department of Medical Biometry and Epidemiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany