ABSTRACT
This chapter considers theories generated in the frameworks of various academic disciplines about health and illness. A formal, comprehensive definition of health was adopted in 1946 in the original constitution of the World Health Organization: "Health is a state of complete physical, mental, and social well-being and is not merely the absence of disease or infirmity." Many people think of health as solely being the absence of illness. A number of investigators studied the development of children's conceptions of health and illness. One of the more classic medically oriented theoretical approaches toward understanding health has its origins in the field of virology. Research in the field of psychology has devoted considerably more attention to developing theoretical models of health that account for the influence of many different variables. It has become clear that the majority of theoretical models of health and illness lack a developmental approach, especially one that incorporates a life-span developmental perspective.
