stress and the immune system

KECOLT- GLASER ET AL (1984)

Natural experiment

Investigated the effects of a natural stressor on the immune system

studied 75 MEDICAL STUDENTS

Took blood samples one month before their final exams and one on the first day of their exams- could have participant effects - taking blood makes more people stress

she gave out questionnaires to measure life events and loneliness- produces quantitive data, gives accurate results

she found that there was a reduced Natural Killer cell activity in the high stress sample compared to the low stress sample

COHEN ET AL (1991)

Investigated the impact that general life stressers had a vulnerabilty to the common cold virus

384 participants

completed questionnaires

they completed three which were about- the number of stressful life events they had experenced in the previous year, how stressed they felt and if they were experiancing any negative emotionsAll three scores were then combined to get one score called the stress index

then they gave the participants a nasal drop that contained the common cold virus

82% of participants became infected

after seven days the actual number of participants whose infection developed into colds was recored

found that falling to fight off the virus was positivelt correlated with stress index scores

shows that life stress and negaive emotions reduce the effectiveness of the immune system, leaving participants less able to resist viral infection

WEAKNESS= RESEARCH IS CORRELATIONAL

in both studies the IV/ co- variable occured naturally

We are unable to manipulate stress in participants and so will never be able to test stress and the immune system in a controlled lab settinf, controlling the EV's.

means that we cannot identify the cause and effect- we can only assume that stress depletes the immune system

WEAKNESS= OF THE METHODS

Kiecolt- Glaser only measured the immune functioning and not the imapct this would have on health

Cohen only measured the impact on health  but no direct measure of immune functioning

Problem because both studies separately cannot show that stress leads ti a depleted immune system which leads to illness

therfore based on thses studies we cannot say for certian that stress does affect immune functioning, which affects illness

Kiecolt Glazer only measured one part of the immune system

lots of other parts of the immune system that could be depleted in people who feel stressed apart from their NK cells.

Problem because Kiecolt- Glazer assumed that if they had lots of NK cells their immune system was working fine, however another part of their immune system might not be working fine.

Therefore we cannot use Kiecolt Gazer's findings as evidence of depleted immune functioning- they did not measure all of the immune system

Sample used by Kiecolt Glazer was biased

She only used a small sample size and they were all medical students

cannot say that medical students will suffer from the same stressors as other people, or deal with them in the same way

therefore this study lacks population validity- we cannot say that stress in other groups of people will have the same effect on the immune system

EVANS ET AL measured the immune system of students who were all giving a talk to other students, then sitting their exams

found that students had an increase in slgA when giving talks, but had a decrease in it during exam period

they called this increase up- regulation and the decrease down- regulation

therefore it's too simple to see if stress has a negative effect on the immune system