This document discusses the changing concepts of health over time. It begins by defining health according to the World Health Organization as a state of complete physical, mental and social well-being. It then outlines 4 changing concepts of health: 1) the biomedical concept which views health as the absence of disease, 2) the ecological concept which sees health as a dynamic equilibrium between humans and their environment, 3) the psychosocial concept which recognizes social, psychological and other non-biological influences on health, and 4) the holistic concept which synthesizes all previous concepts and views health as involving overall wellbeing.