Stress, coping behavior and resistance to disease.

Psychosocial factors affect resistance to a wide variety of diseases in animals. Stimuli often assumed to be noxious (e.g., electric shock, isolation housing) have been found to exert either potentiating or protective effects on an animal's response to potentially pathogenic stimulation. This variability has often been attributed to the influences of these stimuli on aspects of neuroendocrine or immunological function which are related to specific forms of pathogenic stimulation. The impact of a particular form of stimulation on the physiological state of the organism is also determined by the ability of the animal to cope with the stimulus environment. Factors shown to influence have included: (a) other aspects of the immediate environment at the time of stimulation; (b) prior experience with the same or other forms of stimulation; (c) the animal's ability to control its relationship to the stimuli by learning to escape or avoid them; (d) the availability of relevant feedback regarding stimulus onset (e.g., warning signal), and (e) the stage of the disease process at which stimulation is imposed. These findings by various investigators indicate that it may be inappropriate to place a priori value judgements on any form of psychosocial stimulation or stress either as conceptually or operationally defined. The adaptive value of the psychosocial environment will depend upon its perception by the animal, the animal's ability to cope with the stimulus environment, and the particular disease system being studied.