In the context of health sciences, particularly in the Anglo-American sphere, the relationship between spirituality, religiosity, and mindfulness with quality of life and health is being researched. Many empirical studies demonstrate that this relationship can be medically relevant. The importance of spirituality is increasingly recognized not only within palliative and pain medicine but also in the fields of health psychology, quality of life, and health services research. At the intersection of subjectively perceived significance and empirically demonstrable health relevance lies the connection to transdisciplinary research questions, which this book aims to address. It is written for practitioners (doctors, psychologists, analysts, and caregivers) as well as for students and researchers in the fields of medicine, nursing science, and psychology.