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Key Study: Stress and the Immune System

Janice Kiecolt-Glaser, Warren Garner, Carl Speicher, Gerald Penn, Jane Holliday & Ronald Glaser (1984)

6 January 2013

AIMS: The researchers aimed to establish a link between stress and reduced immune system functioning. This was based on the assumption that the body’s response to stress decreases immune functioning (immunosuppression). They aimed to establish a difference in the way the immune system responded according to high or low stress levels. They also aimed to see if other factors such as psychiatric symptoms, loneliness (social isolation) and life events were associated with immune functioning.

PROCEDURE (METHOD): 75 first-year medical students (49 male and 26 female) volunteered to take part in a natural experiment - the naturally-occurring independent variable (IV) being going from a pre-exam state to a during-exams state - with a repeated measures design. One month before their final exams (low-stress condition) the students gave a blood sample and completed questionnaires measuring psychiatric symptoms, loneliness and life events. On the first day of their finals after the students had complete 2 of their exams (high-stress condition), the students again gave a blood sample and completed the same questionnaires.

FINDINGS (RESULTS): Natural killer and T cell activity - indicators of immune functioning (the dependent variable) declined between the low and high stress. The findings from the questionnaires revealed that immune responses were particularly suppressed in participants who reported they were experiencing psychiatric symptoms, loneliness and/or stressful life events. The psychological factor with the greatest impact was loneliness.

CONCLUSIONS: The research shows that stress is associated with immunosuppression and that the effect is stronger when there are multiple sources of stress, with loneliness having the greatest effect.

CRITICISMS (EVALUATION): As this was a natural experiment and the IV was not manipulated or isolated, many psychologists and other scientists would argue cause-and-effect cannot be inferred from the study - whatever Kiecolt-Glaser et al may say. Thus, only a correlation between increased stress and reduced immune system functioning can be stated with real confidence.

Additionally, it is important to note that the functioning of the immune system of nearly all the students - even those in the high stress condition - was within what would usually be considered ‘normal’ parameters. Besides which natural killer and T cell activity are not the only measures of immune system functioning. Thus, it may be stretching the argument to say immune system functioning was definitely impaired in the high stress condition.

Then there are the obvious criticisms that the sample size was small, unbalanced in terms of gender mix and composed only of medical students - all of which raises doubts as to generalisation of the findings.

While Kiecolt-Glaser et al’s conclusions, on the basis of this study, can be criticised, it should also be noted that Kiecolt-Glaser has led a series of studies, using different sample groups and different methodologies, all of which tend to support the assumption that increased stress is related to reduced immune system functioning.