Role of Stress in Illness (AQA A-Level Psychology): Revision Notes
Role of Stress in Illness
Stress can have profound effects on physical health, particularly through its impact on the immune system and cardiovascular system. When stress becomes chronic, it can lead to serious health problems through a process called immunosuppression and by contributing to cardiovascular disorders.
Stress and the immune system
The immune system is the body's defence mechanism that protects against illness and disease. It consists of billions of cells that travel through the bloodstream, produced in organs like the spleen, lymph nodes, thymus and bone marrow. The main components include leucocytes (white blood cells) that produce antibodies to bind to and destroy harmful antigens such as bacteria, viruses and cancerous cells.
The immune system is remarkably complex, with different types of white blood cells performing specialised functions. Natural killer cells, T-cells, and B-cells all work together to identify and eliminate threats to the body's health.
How stress affects immune function
Immunosuppression refers to the impaired ability of the immune system to fight illness and disease. Chronic stress reduces the immune system's ability to fight off antigens, making infection more likely. While occasional cortisol production doesn't harm the immune system, continuous production interferes with leucocyte activity and antibody production.
Although cortisol initially helps protect against viruses and heal injuries, excessive cortisol suppresses the immune system, harming the very mechanism that protects us from infection. This creates a dangerous cycle where chronic stress makes us more vulnerable to the very health problems we're trying to avoid.
Stressful events are linked to various illnesses including cancer and chronic fatigue disorder, as well as infections like influenza.
Research evidence on stress and immunity
Research Example: Vaernes & Toniussen (1991)
Study: Norwegian air force personnel Findings: Found a relationship between perceived work stress and complaints related to immune system activity, demonstrating a link between work stress and immunosuppression.
Research Example: Cohen et al. (1993)
Focus: Cold virus susceptibility Method: Participants given the virus were monitored for infection rates Results: Those with high stress scores were more likely to catch a cold, suggesting that stress reduces the efficiency of the immune system.
Evans et al. (1994) found that students giving mildly stressful public presentations had increased levels of sIgA, an antibody that improves the immune system's ability to resist infection. This shows how short-term stress can actually be beneficial to immune system functioning.
Research Example: Kiecolt-Glaser et al. (1995)
Method: Gave small wounds to participants and measured healing time Key Finding: The healing process took longer in women who cared for elderly relatives with dementia Conclusion: Prolonged chronic stress reduces immune system effectiveness, as supported by other measurements of immune system functioning.
Stress and cardiovascular disorders
Cardiovascular disorders are dysfunctions of the heart and blood vessels that are particularly linked to immunosuppression. The body requires continual maintenance to stay healthy, but prolonged exposure to storms damages a building. Similarly, prolonged exposure to stress causes physical damage to the body, especially the heart and blood vessels.
Chronic stress can result in cardiovascular disorders such as hardened arteries, hypertension (high blood pressure) and coronary heart disease, which results from arteries supplying the heart with blood becoming clogged with fatty materials.
Stress can lead to cardiovascular problems both directly through activation of bodily stress systems and indirectly through stressed people's unhealthy lifestyles, including excessive drinking, drug-taking, poor diet and smoking.
Research evidence on stress and cardiovascular disorders
Research Example: Cobb & Rose (1973)
Participants: Air traffic controllers vs other air traffic personnel Findings: Air traffic controllers had higher levels of hypertension, increasing the risk of heart disease Significance: Supports the idea of chronic stress being linked to cardiovascular problems in high-stress occupations.
Krantz et al. (1991) studied 39 people with myocardial ischaemia (a condition where the heart receives reduced blood flow) and their reactions to low-level stress. Those with the highest myocardial ischaemia readings had the highest increases in blood pressure when stressed, suggesting a direct link between low-level cognitive stress and physiological reactions leading to cardiovascular damage.
Rozanski et al. (1999) found that some individuals are hyper-responsive to stressors, as the sympathetic branch of their autonomic nervous system reacts more than in other people, leading to more damage of cardiovascular systems. This shows individual differences in people's reactions to stress and their levels of vulnerability to cardiovascular disorders.
Melamed et al. (2006) reviewed clinical evidence and found that burnout, characterised by physical, emotional and cognitive fatigue resulting from prolonged exposure to work-related stress, was associated with heightened levels of cardiovascular disorders and other cardiovascular-related ailments.
Key study: Kiecolt-Glaser - Effect of immunosuppression in medical students (1984)
Worked Example: Kiecolt-Glaser Study Analysis (1984)
Participants: 49 male and 26 female volunteer first-year medical students
Aim: To study the capability of the immune system in people facing stressful situations. The prediction was that immunosuppression, measured by the amount of natural killer cell activity, would be reduced when stress levels were high.
Procedure: Blood samples were taken one month before final exams and again after the first day of exams. The blood samples were analysed for leucocyte activity, specifically natural killer cell activity involved in fighting off viruses and tumours. Questionnaires were also given, assessing psychiatric symptoms, loneliness and life events.
Findings: Natural killer cell activity was reduced in the second sample compared with the first. Immune responses were weakest in those scoring highly for loneliness, stressful life events and psychiatric symptoms such as depression and anxiety.
Evaluation: Strengths
- The stressors used were naturally occurring rather than artificially induced, making the findings more applicable to real-world situations
- Blood samples provided objective, biological measures of immune system functioning
Evaluation: Weaknesses
- The study used a repeated measures design where participants were compared with themselves on two occasions, but this controls for participant variables such as personality
- It's uncertain whether the stressors caused changes in immune function; other non-controlled situational variables might play a part
- The sample of volunteer medical students is potentially not representative of the general population
Evaluation of stress and illness research
Several important evaluation points apply to research on stress and illness:
Individual differences play a crucial role in vulnerability to stress-related illness. Research shows differences based on personality type, gender and age. For example, Johnson & Sharma (2001) found evidence of immunosuppression in female rats but not males, while Lindemann et al. (1978) found immunosuppression increased with age in mice.
Correlational evidence dominates this field, making cause and effect relationships difficult to identify. Other factors like unhealthy lifestyles of stressed individuals (smoking, drinking) may also contribute to illness.
Longitudinal studies involving measurement of immune system functioning over extended periods would be required to establish clear causal relationships, but changes in immune system functioning take time and may not be immediately identifiable.
Ethical considerations prevent researchers from conducting experiments to determine whether stress directly causes cardiovascular disorders or other serious illnesses.
Practical applications exist, as findings from stress and illness research are used by health practitioners to help anticipate problems occurring as a response to stressful incidents and to develop appropriate therapies.
Key Points to Remember:
- Immunosuppression is the key mechanism by which stress leads to illness - chronic stress weakens the immune system's ability to fight off disease
- Research consistently shows links between stress and both immune system dysfunction and cardiovascular disorders through multiple studies
- Individual differences in personality, gender and age affect how vulnerable people are to stress-related illness
- Most evidence is correlational rather than causal due to ethical limitations in research design
- Both direct biological effects and indirect lifestyle factors contribute to how stress leads to illness