Stress and the Immune System

Stress and the Immune System
aim: to study the effect of stress (exams) on the immune system. They wanted to test the hypothesis that stress reduces immunity by seeing if there is a difference in immune response between two conditions (high and low stress). They were also interested to see if other factors affected immunity, such as psychiatric symptoms, loneliness, and life events. procedures: ? 75 first year medical students (self-selected sample) volunteered to participate. It was a natural experiment as the IV (level of stress prior to exams) was not manipulated by the investigators, but occurred naturally. ? The investigators took blood samples 1 month before the final exams (baseline measurement of low stress) and on the first day of the final exams (high stress condition) in a repeated measures design. ? The numbers of natural killer cells and T cells were counted in the two samples, and used as the indicators of immune functioning (the DV).
Questionnaires were also used to assess 3 areas of behavioural functioning: any psychiatric symptoms, degree of loneliness, exposure to life events findings: ? The number of natural killer cells had significantly declined in the stress sample ? The reduced immune response was most strongly associated with students who reported the most stress e.g. those who felt the most lonely, those who experienced stressful life events or who suffered from psychiatric symptoms like depression and anxiety conclusions: ? The decline in natural killer cells in humans supports the earlier animal studies showing that stress suppresses the immune response ? Immunosuppression was strongest when there were additional sources of stress ? The study shows that various sources of stress (eg. exams, psychiatric illness, loneliness and life events) have a similar depressing effect on the immune system criticisms: ? This was a natural experiment, so cause and effect cannot be determined with certainty as the IV (stress level) was not deliberately altered. Uncontrolled factors could have caused the differences, such as individual differences in immune functioning, diet, lifestyle, personality type etc. At best, the results have suggested an association (a negative correlation) between stress and immune suppression. ? The measure of immune function (number of natural killer cells and T cells) is an objective measurement that cannot be biased in a subjective way (eg. opinion) by the investigator. Neither can immune response be biased by experimenter expectancy. These factors increase the validity of the measures, although there still may be other kinds of bias eg. the confounding variables due to individual differences.

Stress and the Immune System 8.6 of 10 on the basis of 2546 Review.