Stress and the Immune System

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Cohen's Colds

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


  • 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

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Cohen's Colds - AO2

  • - 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
  • - The study used a a large sample
  • C - This increases the reliability of the study and is more representable of the target population
  • - 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
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Kiecolt-Glaser's Medics

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


  • 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


  • 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

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Kiecolt-Glaser's Medics - AO2

  • - 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
  • - 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
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