Abstract
Religion and medicine have a long, intertwined, tumultuous history, going back thousands of years. Only within the past 200–300 years (less than 5 percent of recorded history) have these twin healing traditions been clearly separate. This series on religion and medicine begins with a historical review, proceeding from prehistoric times through ancient Egypt, Greece, and early Christianity through the Middle Ages, the Renaissance, and the Age of Enlightenment, when the split between religion and medicine became final and complete. Among the many reasons for the continued separation is that religion may either be simply irrelevant to health or, worse, that it may have a number of negative health effects. I review here both opinion and research supporting this claim.