Cohen (1993)
Aim: to investigate if life stress and negative emotions reduce immunity. He investigated role of general life stress on vulnerability to common cold.
Procedure: 394 p's completed questionnaire on number of stressful life events they had in past year.
Also rated degree of stress and their levels of negative emotions e.g. depression.
The scores were rated in 'stress index'.
P's were then exposed to the common cold.
Results: 82% infected after 7 days.
Conclusion: Chance of developing cold correlated with stress index scores.
+/-:
- This was an indirect study and there were no measures of immune function.
Evans and Eddington (1991) found the reliability of developing a cold was correlated with stress in the preceding days.
-It measures health outcomes showing a relationship between life stress and illness.
Unethical
Low population validity
Demand characteristics
No manipulation of IV and so cause and effect can't be confirmed.
This study doesn;t tell us which element of stress index is important.
Require medical supervision.
P's should be in good health prior.
Kiecolt-Glazer (1984)
Aim: interested in naturalistic life stressors and their impact on measures of immune function.
Procedure: 75 medical students preparing for exams.
As an index of immune function, they measures natural killer (NK) cell activity (part of immunity) via blood samples.
Samples taken one month before exams (low stress) and during the period (high stress).
P's completed questionnaire on experience of negative life events and social isolation.
Results: NK activity reduced in high stress samples compared to low stress samples.
Greatest reductions were in students with higher levels of social isolation.
+/-: significant reductions seen in this study are too small to increase chance of stress relayed illness.
No manipulation of IV so cause and effect relationship cannot be confirmed.
Would require medical supervision.
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