Acute Stressors: Examination Stress (1)
Keicolt-Glaser et al. (1984)
- Natural experiment investigating weather the stress of short-term stressors (exams) had an effect on immune system functioning in medical students.
- Blood samples were taken one month before examinations (low stress) and during the exam period its self (high stress).
- Immune system activity was measured by measuring NK cell activity in the blood.
- NK cell activity was significantly reduced in the second sample compared to the first.
- This suggests that short term, predictable stressors reduce immune system functioning, increasing the vulnerability of illness.
- +ve's = quantifiable results from concentrations of NK cells.
- -ve's = medical students are not average students, does not take into account other stressors.
Acute Stressors: Examination Stress (2)
Marucha et al. (1998)
- Did a mouth punch biopsy on students during the summer and 3 days before exams.
- The mouth punch created a small wound in the mouth.
- Marucha timed how long it took for the wound to heal.
- Wounds in the exam period took 40% longer to heal than those during the summer holidays.
- Shows that stress has an effect on the time taken for wounds to heal.
- +ve's = Shows visually how stress affects the immune system.
- -ve's = Students may just have low white blood cell levels, so wounds take longer to heal anyway.
Chronic Stressors: Relationship Stress
Malarkey et al (1994)
- Studied 90 newly-wed couples over a 24-hour period.
- They were asked to discuss and resolve marital issues that are likely to produce conflict (i.e. financial discussion).
- Marital conflict produced significant changes in the levels of adrenaline and noradrenalin, which could lead to poorer immune functioning.
Stress: Enhancing the immune system
Evans et al (1994)
- Looked at the activity of the antibody - slgA - which helps protect against infection.
- Evans arranged for students to give talks to other students (mild but acute stressor)
- During the talk to other students - levels of slgA increased.
- slgA levels during examinations (last over several weeks) decreased.
- Stress may have two effects on the immune system.
- Up-regulation for short-term acute stress.
- Down-regulation for chronic stress.
Segerstrom and Miller (2004)
Meta-analysis of 293 studies over 30 years
- Short-term, acute stressors can boost the immune system, prompting to ready itself for infections or other challenges to the integrity of the body.
- Long-term, chronic stressors led to suppression of the immune system - the most chronic stressors were associated with the most global suppression of immunity.
- The longer the stress, the more the immune system shifted from potentially adapted changes to potentially detrimental changes.
Evaluation: Lazarus (1992)
Lazarus (1992) suggests there are various reasons why a relationship between stress and illness is difficult to establish.
- Health is affected by many different factors (including genetic influences, lifestyle, etc.). As a result, there maybe little variance left that can be accounted for by stress.
- Health is generally fairly stable and slow to change. As a result, it makes it difficult to demonstrate that exposure to particular stressors have caused a change in health.
- To demonstrate how stress affects long-term health would involve continuous measurement over time. This would be expensive and impractical, therefore most research has concentrated on relatively short periods of time.