Stress-related illness: The immune system

Kiecolt-Glaser et al:

Aim: whether the stress of short term stressors such as examinations had an effect on imune system functioning in medical students.

Procedures: blood samples one month before (low stress) and and during exam period (high stress). Immune system functioning was assessed by the NK cell activity in the blood samples.

Results: NK cell activity was significantly reduced in the second blood sampl during examinaions compared to the sample before the exams, suggesting predictable stressors reduce immune system functioning increasing vulnerability to illness.

Conclusions: This is a natural experiment however cannot be generalised as it only tests medical students who lead a different lifestyle than other students which may be the cause for their low NK cell activity.

Kiecolt-Glaser et al:

Aims: The impact of interpersonal conflict on wound healing.

Procedure: Comparing women separated from their partners with matched married controls.

Results: Blister wounds on the arms of married couples healed more slowly after they had discussions which were conflicting rather than supportive. Also women who had separated in the last year had poorer immune systems.

Conclusion: There may have been extraneous variables causing the women to have poorer immune systems. Also some women my benefit from separating from their partners. These result may lack ecological validity as they cannot be generalised to all separated women and they reasons for separation may have an impact on the results.

Evans et al:

Aim: Whether stress can enhance the immune system.

Procedures: Looking at the activity of a particular antibody SigA which coats mucous surfaces around mouth, lungs and stomach and helps protect against infection. Evans arranged students to give talks to other students (mild but acute stress).

Results: The students showed an increase in SigA whereas levels of SigA decreased during examination periods.

Conclusion: Stress may have 2 effects on people positive effects for short term acute stressors and negative effects for long term chronic stressors. This experiment may lack validity because they findings counter act each other.

Lazarus suggested there are various reasons why a relationship between stress and illness is difficult to establish:

• Health is affected by many different factors
• Health is generally stable and slow to change making it difficult to demonstrate that exposure to particular stressors have caused a change in health.
• Measuring long term effects of stress would involve continuous measurement over time and so is expensive and impractical also most studies are carried out over short periods of time which means the results wouldn't be fully valid.

• Research has shown consistent age and gender differences in the stress and immune system relationship.

• Women show more adverse hormonal and immunological changes in their reactions to marital conflict.

• As people age stress has greater effects on immune system functioning making it harder for the body to regulate itself.