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The two pathways
- Sympathomedullary pathway - acute stress
- Pituitary-adrenal system - Chronic stress
The Sympathomedullary Pathway
The immune system two studies:
- Cohen et al
- Kiecolt-Glaser et al
Cohen et al
- used questionnaires to obtain stress index scored for 394 participants
- Participants exposed to common cold virus 82% became infected with virus.
- Chance of developing a cold was significantly correlated with the stress index score
Kiecolt-Glaser et al
- Natural experiment
- Blood samples were taken from 75 medical students one month before exam (low stress condition) and during exam period (high stress condition)
- Measured natural killer cell activity in blood samples as an indication of immune function
- Findings: - natural killer cell was significantly lower in the 2nd condition
- Shows short-term stressors reduce immune system functioning.
Immune system AO2
- sample were all volunteer medical students - limits generalisation of findings. BUT Kiecolt-Glaser found similar results with other social groups.
- K-G measured the natural killer cell activity to measure the immune function -only one component of a very complex system
- A range of variables may effect immune system - e.g. inds general health lifestyle - THEREFORE to simplistic to suggest relationship between stress and the immune system.
- Furthermore it is important to distinguish between short term and long term stress.
Life changes studies
- Holmes and Rahne
- Rahne et al
Rahne et al
- over 2700 American male sailors were giving the SRRS questionnaire to complete just before they left for their tour of duty
- When a sea, health records were kept for each participant and an illness score was calculated
- Found a small significant positive correlation of 0.118 between the mens LCU's scores and illness scores
- Researchers concluded that experiencing life changes/events increases the likelihood of illness
Rahne et al AO2
- used correlation analysis - so its not possible to conclude cause and effect
- Its simplistic to see the relationship between life events and illness as a casual one. Studies have found that personality is a mediating variable in the relationship between life changes and illness
Holmes & Rahne
- Developed SRRS scale to asses to impact of life events
- Life events are assigned to life changes units (LCU) from 100 to 11
- A person stress score is the sum of all the life changes units they have experienced within a period of 12 months.
- Score of 300 or over meant that there was an 80% chance of developing a serious physical illness in the following year
Holmes & Rahne AO2
- Limitation is that the SRRS scales assumes that the same life event would have the same amount of impact on different people. -This is unlikely and over simplistic
- Does not distinguish between positive ad negative events - other research shows that negative events are more stressful then positive events
- Life changes are relatively rare - daily hassles may well be a more significant source of stress
DeLongis believed that life also contained positive events known as uplifts that could counteract the negative effects of daily hassles - he made a scale
DeLongis et al 1982 (first study)
- Was supporting evidence for the scale
- Gave the uplifts and hassles scale to 100 participants between the ages of 45 and 64
- For a period of a year participants completed monthly measures of hassles and uplifts, life events and health status
- Found hassle scores has a higher correlation with health problems than life events
DeLongis et al 1988 (second study)
- gave 75 married couples both a life event questionnaire and the Hassles and Uplifts Scale. The couples were assessed 20 times over a six month period
- Found no relationship between life events and health but there was a significant positive correlation of +59 between hassles and next day health problems such as flu, headaches and sore throats
Daily hassles AO2
- results are consistent with findings that suggests there is a distinction between the effects of short term and long term stress - chronic stress being more serious.
- But rating the hassles is completed retrospectively (old data) - memories may not be reliable because recollections are affected by current state of mind.
- Correlation doesn't show causation - could be other variables (personality).
- Theres two things that cause it: -lack of control
- - work overload
- Lack of control was Marmot et al
- Work Load Johannason et al
Marmot et al - Lack of control
- Studied 7000 civil servants over a 5 year period to see their health status (longitudinal study)
- Those in highest grades developed fewest CVD (reported greater control over their work and good level of social support)
- Those in lowest grades developed the most CVD (reported less control and had the poorest level of social support)
Marmot et al AO2
- Large sample size - able to generalise the study more also it was a longitudinal study which allows the study to prove more accurate results.
- Individual differences - lower grade workers may have had other characteristics in common + higher grade may have hardy personality - see work as a challenge
- Correlation does not prove causation.
Johannson et al - Work load
- Did a study at a Swedish saw mill.
- Compares 14 finishers (high risk as their productivity determined wages of entire factory) with 10 cleaners (low risk)
- finishers (high risk group) had higher levels of stress hormones, stress-related illnesses and absenteeism
Johannson et al AO2
- Small sample which is not representative as they all worked at a specific Swedish saw mill
- Difficult to separate the effects of different stressors - there are many other work place stressors (noise, temperature)
- Only male sample - cant generalise
Personality factors - what is Type A/B?
- Friedman and Rosenman described type A personality as possessing 3 major characteristics (HIC):
- Types B has an absence of these characteristics
Type A/B continued
- Type A individuals respond more quickly to stressful situations
- Stress activates the sympathetic branch of the ANS - leads to rise in BP, HR and constriction of blood vessels
- The release of stress hormones results in the increase of fatty acids in the bloodstream. Cholesterol particles clump together leading to clots in blood and artery walls -increase CVD
- Type B are less likely to get CVD
Friedman and Rosenman Study
- natural experiment
- 3500 Californian men (39-59yrs) given qs and structured interview and identified as type A, B or X (mixture) - all were free from CHD at start of research
- Lifestyle factors such as obesity and smoking were controlled for
- studied over a 8 1/2 year period
- 7% of Sample had developed some signs of CHD - 70% were type A inds
- Type A men also had higher BP and Cholesterol levels
- Concluded that types A beh increases vulnerability to heart disease
Type A/ B AO2
- A lot of research has found that Type A/B is not a strong predictor of heart disease - only half the studies have showed a significant link to CHD
- Its not clear what aspect of Type A is most strongly associated with CHD
- One study found that hostility was more linked to CHD than overall type A/B score
- The study is culturally specific (Californian) and gender specific (males)
- Correlation doesn't prove causation
- Kobasa and Maddi 1977 - claim some people are more resistant to harmful effects of stress as they have hardy personalities (the 3 C's)
- Control -feel in control of events in their lives
- Commitment - involved in the world around them and feel a sense of purpose and involvement
- Challenge - stressful situations are challenges to be overcome rather than obstacles
Hardiness AO2 -study
- Kobasa 1979 -studied 800 American middle managers who experiences a high level of life events in the past 3 years (SRRS scale)
- assessed hardiness using a hardiness test - those who were rarely ill scored high on all 3 C's of the hardy personality
- Strengths: - research can account for studies that haven't found a correlation between type a/b and CHD
- Real life application of this research - Hardiness training has become more widespread (army)
- Limitations: - may be more simple than Hardiness -some research shows its simply due to control
- Relies on self-report methods - issues with demand characteristic and social desirability - so reduces questionnaires reliability