Consultation-liaison psychiatry is a psychiatric subspecialty dealing with the relationship of mind and body and the effects of mental, social, and environmental factors on physiologic function. Since the time of the ancient Greeks, physicians, philosophers, and theologians have disputed whether the mind and body are single or dual entities. The work of Cannon (flight or fight), Selye (general adaptation syndrome), and others in the 19th and 20th centuries began to provide scientific evidence of the relationship. A major proponent of this view was Helen Flanders Dunbar, M.D., who began to research what was termed psychosomatic medicine and provided a foundation for consultation-liaison psychiatry.