Brady (1958) supported the GAS with his experiment on monkeys. Pairs of monkeys were linked up to some equipment, which gave electric shocks. Shocks were given over a 6-hour period at 20-second intervals, continuing over several weeks. One monkey from the pair (the executive) could prevent shock to both monkeys by pressing a lever, the other (yoked) monkey also had a lever but pressing it did not stop the shock. The results showed that the executive monkeys developed ulcers while the yoked monkeys did not. Brady came to the conclusion that the executive monkeys had to remain constantly vigilant to avoid being shocked, while their partners could do nothing to influence the situation. Constant vigilance is highly stressful, and this stress led to physical illness.
There is a very crucial criticism for this experiment. It lacked the factor of individual differences. The monkeys who had learned that pressing the levers became executives and the rest were left as yoked.
Links between stress and physical illness have been investigated. Because stress effects the functioning of the immune system, people are more likely to catch colds after stressful experiences. Cohen et al (1991) proved this with his research. Healthy volunteers (154 men and 266 women) were injected with a common cold virus or a harmless salt solution. They were also given a stress index based upon the number of stressful events they had experienced in the past year, the extent to which they felt able to cope, and the incidence negative feelings such as anger and depression. The results showed that almost all of those that were injected with the common cold virus showed signs of infection, but only a third developed colds. There was a positive relationship between stress index and cold symptoms even when other factors (such as diet, age, and exercise) were taken into account. This led to the conclusion that there is a positive relationship between stress and vulnerability to infection.
This experiment can be criticised. Firstly Cohen had given a stress index, this isn’t fair, as someone’s perception of stress can be different from another so some people might not consider it a stressful event, hence making it in accurate. Also he used more men than women. This can be considered unfair as women may cope with stress at a different level to men and also that not all people exposed too high levels of stress developed disorders or a lot of negative emotions.
Janice Kiecolt-Glasser (1993) developed Cohen’s theory and met all the criticism. Her group devised ways of measuring the activity of the immune system and concluded that immunosuppression (low immune activity) was at high risk in the following groups; unhappily married women, recently separated women, long-term carers for Alzheimer patients and medical students taking examinations.
Since stress depresses the immune system, it reduces the body’s ability to fight attacks in the form of infections and viruses. A weakened immune system may also lower resistance to cancer cells. Jacobs and Charles (1980) asked cancer patients about stress in their lives before cancer was diagnosed. The results were that patients often reported higher than normal levels of stress. The conclusion was that the experience of high levels of stress might be linked to the development of cancer.
I have proved, after looking at different findings from different researchers, that stress does have an affect on the immune system. To what extent we do not know as there has not been any conclusions on this.
