Kiecolt-Glaser et al 1984

To find out the effects of stress on the number of Natural Killer (NK) cells there are in the immune system.

This was to be achieved by using a Naturalistic Experiment.

They used 75 medical students who were preparing for their final examinations.

Measures of NK cell activity were recorded from blood samples one month before the exams (low stress) and during the exam period (high stress).

Participants also completed questionnaires on experience of negative life events and social isolation.

Findings were that NK cell activity was significantly reduced in the high stress samples, compared to low stress samples.

In addition, the greatest reductions were in students reporting higher levels of social isolation.

They concluded that examination stress (a brief naturalistic stressor) reduced immune function, making people potentially more vulnerable to illness and infections.

The effects are more noticeable in students experiencing higher levels of isolation.