Stress and the immune system: (Kiecolt-Klaser et al, 1984)
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
