The present study is a collection and systematic summary of several papers which were published over the last five years. The publication of this volume would not be possible without the help of many people. My special thanks go to Prof. Dr. Klaus Hurrelmann, former head of the Department of Prevention and Health Promotion at the School of Public Health and now Professor of Public Health and Education at the Hertie School of Governance for his loyal, friendly and stirring support and collaboration. He has indeed broadened my view on research in adolescence and public health. Further, I would like to thank my c- leagues who worked with me on the different papers, first of all my former colleagues from the University of Bielefeld: David Bowles, Dr. Michael Erhart, Dr. Anja Langness, Prof. Dr. Anja Leppin, Dr. Rafael Mikolajczyk. I also wish to thank my German colleagues and co-authors for their valuable advice and support: Prof. Dr. Andreas Klocke (FH Fra- furt/Main), Prof. Dr. Wolfgang Melzer (TU Dresden) and Dr. Andreas Mielck (Helmholtzzentrum, Munchen). My special thanks go out to Dr. Thomas Lampert (Robert Koch-Institut, Berlin) for his friendship, his interest and engagement which lead to many joint ideas, projects and publications. Further, I express my sincere thanks to my international colleagues who worked with me on the different studies summarized in this v- ume: Prof. Dr. Candace Currie (University of Edinburgh, UK), Prof. Dr.