Stress may be regarded as a process of transactions in which the resources of the person are matched against the demands of the environment. The individual's appraisal of the importance of the demands are reflected in the bodily resources mobilized to meet them.

One of the beliefs underlying the use of physiological and chemical techniques in human stress research is that the load that a particular environment places on a person can be estimated by measuring the activity of the body's organ systems. Technological advances, along with progress in the biobehavioral and biomedical sciences, have made new methods available for investigating the interplay between mental and physical processes. Much of what was previously the subject of speculation can now be recorded and measured, and as more of what happens in the different bodily organs becomes accessible to measurement, the effects that mental and physical processes have on one another become increasingly clear. We can record changes in heart rate that accompany changes in the environment. We can show how psychological processes are reflected in the activity of the brain, in cardiovascular functions, in hormonal activity and we can see how hormonal changes affect changes in mood, how blood pressure rises to challenge and how the alertness of the brain varies with the flow of impressions transmitted by the sense organs.

How dangerous is stress?

There is a general agreement that mental stress may increase the risk of ill health and affect the course of both bodily and mental disorders. However, the biological mechanisms by which stress translates into disease are still obscure. Relationships can be seen between stress and diseases such as myocardial infarction, high blood pressure, gastro intestinal disorders, asthma and migraine. However, it is only occasionally that a particular mental factor can be identified as the specific cause of a disease. As a general rule the psychological aspect is merely one thread in a complex fabric in which genetic components, environmental conditions, and learned behaviours are also interwoven.

This lack of clear picture of the links in the causal chain between stress and disease hampers our efforts to prevent harmful stress responses. However, we know a great deal about eh mobilization of stress hormones under conditions of underload and overload, and although it is still not known when such stress responses lead to ill health it is agreed that they should be treated as early warning signals. Moreover, we also know a great deal about how stress that is liable to impair health can be counteracted. Stress responses can be dampened, for instance, by providing opportunities for personal control, which can then serve as buffer, warding off potentially harmful effects of, for example, overload at work.