Stress

Abstract

‘Stress’ is a familiar concept that upon analysis becomes a very difficult term to define, for it is necessary to consider the stimulus, the internal reactions to the stimulus, and the responses of the individual to the stimulus. Some assess stress on the basis of the changes in adrenal hormone secretion produced by a particular stimulus, thus focusing attention upon the response rather than the stimulus, but individuals do not all react in the same way so that a stimulus that is stressful to one is ignored, disregarded or not reacted to by another. Other investigators prefer to regard a particular stimulus (which they then call a stressor) as uniformly stressful, even though some individuals may not react in the anticipated manner, and some hardly at all. Surgery powerfully activates the hypothalamo—pituitary—adrenocortical system, and thus raises the output of the adrenal steroid cortisol, but the prospect of surgery can be just as effective, as can admission to hospital, the prospect of a college or university examination, or the expectation of exhausting physical exercise. On the one hand the physiological response to stress, as after injury, is of greatest concern, while on the other psychological factors, as in the assessment of the degree of personal threat, is paramount. Because of difficulties in classifying the stimuli, greater regard has been paid to the physiological response, but with repeated exposure to stress adaptation may occur, so complicating definition of a stress.