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. Also, it appears that the course and manifestations of any disease can be influenced to some extent by activities of the nervous and endocrine systems that are initiated by the central nervous system in response to information from the social and interpersonal environment. On the other hand, the theoretical explanation of how 'stress' causes disease, which was developed in the 1930s and 1940s and based on a hypothetical 'state of stress' within the organism, as a model derived from engineering concepts, is clearly incorrect. The relation of an organism to its environment is, in large measure, a communicative interaction. Its response to a threat to its integrity is based upon the evaluation of the information received. This response is not random and non-specific, but directed, and it is as highly specific as the effector mechanisms of the organism can make it.