In addition, the immune system may have been affected by other factors in the carers’ lives such as drugs, alcohol, caffeine, nicotine etc. A person’s general health, their diet and physical activity, sleep patterns, age and medication could have all been factors supplementing their stress. The attempt to isolate these factors from the experiments would be controlled; however, it was unlikely that there was complete control over them. Despite this, the weight of the evidence does suggest that apart from short-term acute stress, the experience of stress does suppress the immune system. The relationship of the experiment shows that suppression of the immune system does make the body more vulnerable to illnesses.
Long-term stress can affect the cardiovascular system. Studies have been carried out to test the effect of stress on the heart. Russerk’s study, conducted in 1962, identified the link between stress and heart disease. He outlined two groups, which he thought would experience high levels and low levels of stress. The two high stress groups included a GP and an Anaesthetic; the two low stress groups were Pathologists and Dermatologists. Before the experiments began, questionnaires concerning the general mental and physical health were given to the participants asking them of general health and well-being.
Russerk found that the high stress level groups had a percentage of 11.5% compared to the low stress group which had only 3.2%, compared to the national average. Therefore the low stress groups were less likely to develop heart disease than the high stress groups. Another finding of Russerk’s study showed that if a person had a high stress job (GP, anaesthetic) then they were more likely to develop a heart condition than someone who had a poor quality of diet, lifestyle and poor family background.
Friedman and Rosenman’s study of stress and coronary heart disease was to try and discover whether there is a true link between people with Type A personality (highly active, competitive, aggressive, hostile, impatient, fast talking and thinking) and an increased risk of heart disease. Californian men between the ages of 39 and 59 who were free of any signs of CHD were sampled. Over 8 1/2 years later they were studied and examined for signs of CHD at the end of the period. Findings showed the 7% of men had developed signs of CHD. 2/3 of these men had a ‘Type A’ personality. Type B behaviour consists of temper, patience and knowing one’s limits. They may be ambitious as well; they do not push themselves to the limit.
They concluded that men with type A personalities generally have a higher blood cholesterol level and more adrenaline and noradrenalin in their bodies then men with Type B personalities. Adrenaline and noradrenalin are released as part of the stress response. They in turn produce higher levels of fatty acids in the blood, all of which may lead to the narrowing of arteries, due to the fatty deposits on the artery walls -atherosclerosis.
The term ‘Type A’ and ‘Type B’ personalities are too broad and include many factors. Other studies have claimed that one area of Type A personality called cynical hostility is the part most likely to increase the likelihood of getting CHD. Also, this study only used middle-aged men, which are more likely to develop CHD than young men or women. However, because all the men were chosen from one place, confounding variables are reduced, such as culture. Linked with this is representation. The sample of men used was small, so it was not an accurate representation of the population.
Other studies, which have replicated this one, have shown contradictory findings. Kiercolt et al provided one of the most reliable in proving the relationship between stress and illness. Other researchers have also reported similar findings for the recently bereave (Antoni 1987), and recently, Kiercolt’s group have found reductions in immune functions in couples even after short episodes of marital conflict (Kiercolt Glaser et al 1998). They also found significant increases in release of stress hormones, and interestingly, changes in the stress indicators were greater and longer-lasting in women.
Yet Brady’s study was conducted before the BPS rules, his study still proved that the stress of maybe having the responsibility of delaying shocks stressed the monkeys and caused illnesses. If this research was to be correlated with humans, it still proves that stress causes illness. However, there is evidence, which hasn’t been explained in Brady’s study, such as; did the monkeys suffer psychological problems?