Stress and the Immune System

Aim: Investigate affect of general life stress on vulnerability to common cold as measure of immune function

Procedure:

• 394 Pps completed life questionnaire and rated levels of stress and depression to make stress index
• Were exposed to cold virus and after 1 week recorded how many had a clinical cold

Findings: Positive correlation between stress index and chance of getting cold

Conclusion: Life stress and depression can suppress the immune system

• P - One issue with this study is that it was a quasi experiment and used correlational evidence
• E - As there may have been other factors involved in getting a cold, such as amount of caffine consumed, the results do not suggest a causal relationship
• C - However, it would have been unethical to cause the Pps stress so was only option

• P - The study used a a large sample
• C - This increases the reliability of the study and is more representable of the target population

• P - Another issue is that it is unclear which element of the stress index is the main contributor to immunity suppression
• E - The stress index consisted of three elements, depression, life events and feeling of stress, meaning either one could be main cause
• C - This limits the usefulness of the research

Aim: Investigate affects of short-term stress on immune system

Procedure:

• Natural experiment using first year medical students
• Blood samples taken 1 month before exams then during exam period
• Measured killer cell activity in blood
• Pps completed questionnaire on life stress and loneliness

Findings:

• Killer cell activity reduced in second sample (during exams)
• Students who rated highest level of loneliness had lowest killer cell activity

Conclusion: Short-term, predictable stressors reduce function of immune system

• P - As it was a natural experiment, there was little control over confounding variables
• E - Factors such as sleep pattern and alcohol intake may have also affected the killer cell activity
• C - The lack of control over confounding variables limits the validity of the research

• P - Individual differences effects the validity of the study
• E - Not all Pps will have been stressed by exams, some more than others
• C - This means that exmas may not have been a reliable stressor