Hans Selye's general adaptation syndrome (GAS) and its stages

Hans Selye, in the 1930s, proposed a theory to explain how the body responds to stress through a three-stage physiological process. This model, known as the general adaptation syndrome (GAS), suggests that both animals and humans react to stressors in a predictable pattern, which can ultimately lead to physical illness if the stress persists.

Stages of the general adaptation syndrome

1. Alarm reaction stage - The body initially detects a stressor and reacts by heightening arousal levels. This prepares the individual for immediate action, often referred to as the 'fight or flight' response, enabling quick reactions to threats.
2. Resistance stage - If the stressor continues over an extended period, the body attempts to adapt and manage the situation. Outwardly, it may appear as though the individual is coping normally, but internally, arousal levels remain elevated to handle the ongoing stress.
3. Exhaustion stage - Prolonged exposure to the stressor eventually depletes the body's resources. Signs of alarm may re-emerge, and the individual becomes vulnerable to health issues, which Selye termed 'diseases of adaptation'. These can include conditions like stomach ulcers, high blood pressure, and mental health challenges such as depression.

Evaluation of the general adaptation syndrome

• Supporting evidence - Extensive scientific research backs the existence of these stages, confirming the body's patterned response to stress.
• Limitations in scope - The model assumes a uniform response to all stressors, overlooking variations in individual reactions. For instance, the amount of adrenaline released can differ based on how threatening a person perceives the stressor to be.
• Additional factors - Recent findings suggest other influences, such as specific bacteria, may contribute to conditions like ulcers. However, stress might still play a role by weakening the body's defences, making such illnesses more likely.

The impact of long-term stress on the cardiovascular system

Chronic stress, experienced over a prolonged period, can have serious consequences for the cardiovascular system, which includes the heart and blood vessels. Persistent stress can directly affect this system, increasing the likelihood of severe health conditions.

Effects on cardiovascular health

• Elevated blood pressure - Long-term stress often results in higher blood pressure, a key risk factor for various cardiovascular issues.
• Arteriosclerosis development - This condition, involving the hardening of blood vessels, can be exacerbated by sustained high blood pressure caused by stress.
• Coronary heart disease - Restricted blood flow to the heart, often linked to stress-induced high blood pressure, increases the risk of this disease.
• Severe outcomes - Stress-related cardiovascular issues can lead to life-threatening events such as:
  • Thrombosis (formation of blood clots).
  • Heart attacks (sudden blockage of blood supply to the heart).
  • Strokes (reduced blood flow to the brain, impairing brain function).

Research on stress and cardiovascular health - Krantz et al (1991)

• Method:
  • A laboratory experiment involved 39 participants undertaking stress-inducing tasks, including a numerical challenge, a focus test, and a speech delivery.
  • Blood pressure and the degree of blood vessel constriction around the heart (measured as low, medium, or high myocardial ischaemia) were recorded.
  • Participants were asked to refrain from heart medication before the study.
• Results:
  • Those with the highest levels of myocardial ischaemia exhibited the most significant rises in blood pressure.
  • Conversely, a few participants with minimal or no ischaemia showed only slight increases in blood pressure.
• Conclusions:
  • The findings suggest that stress directly influences bodily functions, potentially heightening the risk of cardiovascular disorders.
• Evaluation:
  • While stress appeared to correlate with these effects, causation remains unproven.
  • The effects might not be exclusive to stressful situations and could occur during relaxed states.
  • Individual differences among participants also influenced outcomes.
  • The artificial lab setting reduces ecological validity, as it may not reflect real-world stress.
  • However, supporting research by Williams (2000) indicates that individuals prone to anger face a greater risk of cardiovascular issues, reinforcing these findings.

The effects of stress on the immune system

The immune system, comprising cells like white blood cells and chemicals, protects the body by targeting bacteria and viruses. Long-term or chronic stress can impair this system, a condition known as immunosuppression, making individuals more susceptible to infections and illnesses.

Mechanisms of immunosuppression

• Reduced immune function - Chronic stress disrupts the immune system's ability to operate effectively, lowering resistance to diseases.
• Increased vulnerability - With a weakened immune response, the body struggles to combat infections, leading to a higher likelihood of illness.

Research on stress and immune response - Brady et al (1958)

• Method:
  • Pairs of monkeys were subjected to electric shocks every 20 seconds during 6-hour sessions.
  • One monkey in each pair, labelled the 'executive', could press a lever to delay the shocks, while the other had no control over the situation.
• Results:
  • The 'executive' monkeys, who had control over delaying shocks, were more prone to developing illnesses such as ulcers and, in some cases, died as a result.
• Conclusions:
  • The illnesses and deaths were attributed to the stress of attempting to avoid shocks, rather than the shocks themselves.
  • This chronic stress likely diminished the immune system's capacity to fend off illness.
• Evaluation:
  • The study raises significant ethical concerns due to the distress caused to the animals, and such experiments would not be permitted today.
  • Results from monkeys cannot be directly applied to humans.
  • The research fails to account for stress in individuals with limited control over their circumstances, such as those in low-status jobs or facing long-term unemployment, who may also experience high stress levels.

Research on stress and wound healing - Kiecolt-Glaser et al (1995)

• Method:
  • In a study with an independent measures design, a small wound was created on the arms of 13 women who were primary carers for relatives with Alzheimer's disease, a highly stressful role.
  • A control group of 13 individuals without such responsibilities was also included for comparison.
• Results:
  • The wounds of the carers took, on average, 9 days longer to heal compared to those in the control group.
• Conclusions:
  • Long-term stress appears to hinder the immune system's ability to facilitate wound healing, demonstrating the impact of chronic stress on physical recovery.
• Evaluation:
  • Supporting evidence from Sweeney (1995) showed similar delays in wound healing among carers for dementia patients.
  • However, differences between the groups could stem from factors like inadequate diet or sleep deprivation, rather than stress alone.
  • The small sample size limits the reliability of the findings, and a larger study would be needed to confirm the results.