RESEARCH INTO THE EFFECTS OF STRESS ON THE IMMUNE SYSTEM

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RESEARCH INTO THE EFFECTS OF STRESS ON THE IMMUNE SYSTEM

KIECOLT-GLASER ET AL 1993

natural experiment

stress of exams affect immune system

75 medical students preparing for final exams

blood samples taken 1 month prior to final exam

bloods taken again during the exam period

measured the activity of the natural killers in the blood samples

students also filled out a questionnaire to assess any psychological variables

e.g. life events and loneliness

significant reduction of natural killer cells in second sample

due to first sample stress=suppressed immune system

greatest reduction in sample 1 for students reporting high levels of social isolation/loneliness

concluded natural stressers reduce

+ high external validity as it was a natural experiment, the stress experienced was real and will affect others who may take exams in a similar fashion.

- a restricted sample as they were doctors in their final year, they may have learnt to deal with stress. we cannot assume therefore that stress affects everyone's immune function in the same way.

COHEN ET AL 1993

394 participants

completed questionnaire on stressful life events in past year

rated their stress levels and negative emotions

stress index created from 3 scores, ranged from 3-12

participants exposed to one of fie cold viruses

administered through nasal drops

diagnosed after 7 days by a doctor

number of participants who developed colds was recorded

all showed signs of infection

82% developed a cold

direct link between stress and illness

those scoring highly on stress index most likely to develop the cold

+high internal validity due to controlled variables such as age, weight and smoking etc. meaning we can be more certain that the development of the cold was less likely to be due to factors other than stress

-unclear cause and effect relationship and so cannot be sure that immune function is affected by stress levels. e.g. does being stressed lead to illness or does illness lead to stress. a cyclic process?