1. Department of Psychiatry and PsychotherapyUniversity of Cologne Medical School Cologne Germany
2. Deutsches Ärzteblatt and Deutsches Ärzteblatt International, Editorial Offices Cologne Germany
3. Center of Clinical Epidemiology, c/o Institute of Medical Informatics, Biometry and EpidemiologyUniversity Hospital of Essen Essen Germany
4. Department of EpidemiologyBoston University School of Public Health Boston Massachusetts