Effects of Stress on Physiology
The physiological consequences of stress and their effects on health have been studied extensively. Research indicates that stress causes physiological changes that have implications for promoting both the onset of illness and its progression.
Stress and illness onset and progression
Stress causes changes in both sympathetic activation (e.g. heart rate, sweating, blood pressure) via the production of catecholamines and the hypothalamus-pituitary adrenocortical activation via the production of cortisol. These changes can directly impact health and illness onset.
1. Sympathetic activation:
The prolonged production of adrenalin and noradrenalin can result in:
- Blood clot formation;
- Increased blood pressure;
- Increased heart rate;
- Irregular heartbeats;
- Fat deposits;
- Plaque formation; and
These changes may increase the chances of heart disease, kidney disease and leave the body open to infection.
2. HPA activation:
The prolonged production of cortisol can result in:
- Decreased immune function; and
- Damage to neurons in the hippocampus.
These changes may increase the chances of infection, psychiatric problems, and losses in memory and concentration.
These physiological changes can be further understood in terms of Johnston’s chronic and acute model of the stress illness link (Johnston 2002). Chronic stress is more likely to involve HPA activation and the release of cortisol. This results in ongoing wear and tear and the slower process of atherosclerosis and damage to the cardiovascular system.
Acute stress operates primarily through changes in sympathetic activation with changes in heart rate and blood pressure. This can contribute to atherosclerosis and kidney disease but is also related to sudden changes such as heart attacks.
Interaction Between the Behavioral and Physiological Pathways
Stress can, therefore, influence health and illness by changing behavior or by directly impacting an individual’s physiology. So far the behavioral and physiological pathways have been presented as separate and discrete. However, this is very much an oversimplification. Stress may cause changes in behaviors such as smoking and diet
which impact health by changing the individual’s physiology. Likewise, stress may cause physiological changes such as raised blood pressure but this is often most apparent in those that also exhibit particularly unhealthy behaviors (Johnston 1989). Therefore, in reality, stress is linked to illness via a complex interaction between behavioral and physiological factors. Further, Johnston (1989) argued that these factors are multiplicative, indicating that the more factors that are changed by stress the greater the chance that stress will lead to illness.
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