Influence of Stress on the Immune System.

by torquec (student)

“Outline and evaluate what research has shown the effects of stress on the immune system”

The immune system is made up of cells and chemicals that seek and destroy bacteria and viruses. When someone is experiencing a stressful situation, all the body's resources are diverted and this suppresses the immune system by stopping the production of white blood cells lymphocytes. Over a long period of time, the person's immune system stops functioning properly and is left open to infection. Short-term stress involves the suppression of the immune system, known as immunosuppression as part of the need to divert all resources into coping with the emergency. Segerstrom & Miller in their Meta review on 293 studies argue that acute-time limited stressors, stressors that may last 5-100 minutes may in fact lead to upregulation. When we become stressed the adrenal glands secrets adrenaline and cortisol into the bloodstream, Adrenaline increases suppressor T-cells which slow down the immune system and decreases helper T-cells which stimulates cells to attack. Also Cortisol is secreted this inhibits the function of phagocytes which engulfs and antigen and decreases the production of lymphocytes especially T-cells.

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Kiecolt-Glaser et al research looks to establish a link between stress and reduced immune functioning; this was based on the assumption that the body’s response to stress decreases the immune functioning. They aimed to establish a difference in immune response between conditions of high and low stress. They also aimed to see if other factors such as psychiatric symptoms, loneliness, and life events were associated with immune functioning. Kiecolt-Glaser et al found that T-Cell activity were declined between the low stress and high stress conditions therefore, the findings confirm the assumption that stress is associated with reduced immune functioning. The findings from questionnaires revealed that immune responses were particularly suppressed in participants who reported that they were experiencing psychiatric symptoms, loneliness or stressful life events. An advantage of this study is that the choice of IV is a long term of stress. In previous studies, stress had been artificially induced, which is likely to produce a different type of stress to stress, which is experienced naturally, Because this was a natural study, there are fewer ethical objections. This was a natural experiment, meaning that the IV was not under the control by the experimenter. As a result, cause and effect cannot be established as the IV is not controlled or isolated. Therefore it cannot be established that stress causes the immunosuppression. The immune system is very complex, and so it is hard to be sure that it’s functioning was actually impaired in the higher stress condition. This means that the reliability and the validity of the measure are questionable.

Cohen et al investigated the role of general life stress on vulnerability to the common cold virus. Three hundred and ninety four participants completed questionnaires on the number of stressful life events they had experienced in the previous year. They also rated their degree of stress and their level of negative emotions such as depression the three scores was then combined into a stress index. Cohen et al found and concluded that life stress and negative emotions reduce the effectiveness of our immune system, leaving participants less able to resist viral infections. They also found that the chance developing a viral infection correlated with stress index scores. This was in indirect study in that there were no direct measures of immune functioning. However it is supported by Evans and Edgerton therefore this increases reliability and strengthen the argument that stress does suppress the immune system. Also there was no direct manipulation of the IV, and so a cause and effect relationship cannot be confirmed. Since this is an experiment, it has high reliability, internal validity and it can easily control other variables that contribute to inaccurate result. Cause can be determined from the effect and the data can be interpreted accurately because the data was collected and measured was quantitive. However, there is still no profound knowledge about immune system yet, so it is hard to firmly conclude that the result is accurate. Also, during the injection procedure, the participants could have increased their stress level because injection can increase one’s sensitiveness. Hence, there is still weakness of this experiment that needs to back up. Also participants should be in good health with no illness or infections prior to the study and participants should be able to give fully informed consent with debriefing afterwards. During the study participants should be constantly monitored to check for any reactions to the viral challenge.

In their Meta review Segerstrom and Miller also analysed studies using a life event questionnaire. These assess the frequency and intensity of a range of life events, for instance, over the previous year. Overall there were no significant changes in immune functioning. However when studies using participants aged over 55, there was a significant relationship between life even stress and reductions in natural killer cell activity. There was no evidence across all studies for gender differences. However Kiecolt-Glaser et al did show that women showed greater reductions in immune function than men in response to martial conflict.