Outline and Evaluate Research Into the Effects of Stress On the Immune System.
Stress is defined as “a state of psychological tension and physical arousal produced by a stressor”. When stress becomes chronic, i.e. it’s not a stressor that has quickly passed which would cause the SAM system to be activated and end in a ‘fight or flight’ response, but the stressor is constantly present making the body respond with the hypothalamic – pituitary – adrenal axis, that is when the immune system is most affected. Constant release of the stress response hormones can affect the immune system as high levels of corticosteroids can shrink the Thymus gland, in return supressing the growth of T cells. The T cells attack and kill the infected cells in the body to prevent he virus spread, so without those cells your body is a lot more vulnerable to infection and disease as your immune system is weak. This kind of constant hormone release, if not dealt with effectively, can lead to a build-up in the lining of the blood vessels and consequently end in a heart attack – atherosclerosis.
One of the studies conducted into the effects of stress on the immune system is that of Kiecolt – Glaser et al (1984) which looked into the stress and immune functioning in students. Their aim was to investigate the link between naturalistic life stressors and their impact on measures of immune function. The experiment was a natural experiment and they used 75 medical students preparing for their final examinations as participants. NK (natural killer) are a part of our natural immunity system so were used as an index of immune function, and their activity was recorded from blood samples taken. These were taken one month before the exams (low stress) and during the exam period (high stress). Participants also completed a questionnaire on experience of negative life events and social isolation. Kiecolt and Glaser found that the numbers of NK cell activity was significantly reduced in the high stress samples than in the low cell, and the greatest reductions were in the students reporting high levels of isolation. They concluded that exam stress (brief naturalistic stressor) reduces immune function, making people more vulnerable to illness and infections. These effects were more noticeable in students experiencing higher levels of isolation.
This study is limited as it was a natural experiment, which in turn affects its validity as they were not able to control all variables, at least not as many as they would in a lab. This means that, in fact, it’s not necessarily the stress from the exams that caused the lower NK cell count. It could have been factors such as alcohol and drug use, possible life events such as death or divorce, or simply the fact that some people may produce more NK cells than others; none of these factors were taken into account. However, because it’s a natural experiment it has very high ecological validity due to the fact that NK cells are produced naturally in everyone, so this has real life application as it can be applied to other people in other stressful situations. On the other hand, this study is limited due to the fact that only medical students were used. This means that the results cannot be generalised to the general public, reducing their validity, as younger students may initially have better immune systems than older people, therefore stress may affect both groups very differently. Therefore the validity of the findings is limited. However, a major advantage of this study is that, in fact, Kiecolt – Glaser used humans. A lot of previous research i.e. Rasmussen 1957 established a link between stress and virus’, but the studies almost always used non-human participants. Because Kiecolt – Glaser used humans, it makes generalising the findings to other humans as they’ve first-hand been able to observe how stress affects humans. This does however cause some limitations in the study, as some ethical issues could be raised. Physical