Stress and disease: the concept after 50 years.

Although there is no generally accepted definition of 'a state of stress' in biological or social systems, biologists and social and behavioral scientists continue to use the term. They communicate meaningfully by describing and measuring sources of stress and their observed effects on living organisms, without attempting to define the intervening variables. Biologists and medical scientists tend to be concerned with sources of stress that are concrete and observable, and can otherwise be considered as 'causes' of illness and injury; social and behavioral sciences tend to be concerned with sources of stress that represent information that arises from outside the person and is mediated by higher centers of the central nervous system. It is clear that such "psychological stresses" can lead to alterations of internal functions down to the biochemical level, and that they are potential 'causes' of disease; but they do not usually act independently of other mechanisms. The central thesis of the stress theory of disease, as elaborated by Cannon and Selye, appears to have been thoroughly established. Disease can be regarded as a phenomenon that occurs when an agent or condition threatens to destroy the dynamic steady state upon which the integrity of the organism depends; and the manifestations of disease appear to be, in large measure, manifestations of the organism's efforts to adapt to, and to contain, threats to its integrity. In this sense, all diseases are to some extent disorders of adaptation.(ABSTRACT TRUNCATED AT 250 WORDS)