Chapter 5 summarizes the extensive body of empirical research studies that identify health impacts of religious practice, identity, and beliefs. These include thousands of epidemiologic, clinical, social, and behavioral studies, as well as investigations from other fields, notably health services research, the biomedical sciences, and psychiatry and clinical psychology. Population-health studies are emphasized, and the latest findings are summarized on the impact of religion, for better or worse, on medical and psychiatric outcomes and rates of morbidity, mortality, and disability, both in the United States and globally, and across religious affiliation. The work of Jeff Levin and his colleagues is highlighted here. Also summarized and critiqued are the controversial clinical trials of healing prayer that have received so much attention since the late 1980s