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Psychology
Chronic Stress and the Body
Cortisol, Allostatic Load, and Disease
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Stress is the body’s response to challenge, threat, or high demand, and it can help a person react quickly in the short term. Acute stress raises alertness, heart rate, and available energy so the body can handle an immediate situation. Chronic stress is different because the stress response stays active too often or for too long. Over time, this repeated activation can affect the brain, immune system, heart, metabolism, and mood.
Key Facts
- HPA axis pathway: hypothalamus releases CRH, pituitary releases ACTH, adrenal cortex releases cortisol.
- Acute stress is short term and adaptive, while chronic stress is repeated or prolonged and can damage health.
- Cortisol helps mobilize glucose for energy, but long-term elevation can increase fat storage and insulin resistance.
- Allostatic load is the wear and tear caused by repeated stress activation without enough recovery.
- Cortisol decay can be modeled as C(t) = C0(1/2)^(t/t1/2), where t1/2 is the hormone half-life.
- Stress management works best when it improves recovery: regular exercise, mindfulness, social support, and consistent sleep.
Vocabulary
- HPA axis
- The hormone pathway linking the hypothalamus, pituitary gland, and adrenal glands during stress.
- Cortisol
- A steroid hormone released by the adrenal cortex that helps regulate energy, inflammation, and stress responses.
- Acute stress
- A short-term stress response that prepares the body to act and usually settles after the challenge ends.
- Chronic stress
- A long-lasting or frequently repeated stress response that can strain body systems and increase disease risk.
- Allostatic load
- The cumulative biological cost of adapting to repeated stress over time.
Common Mistakes to Avoid
- Treating all stress as harmful is wrong because short bursts of stress can improve focus and performance when recovery follows.
- Ignoring recovery time is wrong because the body needs periods of lower arousal to return cortisol, heart rate, and inflammation toward baseline.
- Blaming cortisol for every stress symptom is wrong because stress also involves the sympathetic nervous system, sleep changes, behavior, and social context.
- Using only one coping strategy is wrong because chronic stress usually improves most when sleep, movement, thinking patterns, and support systems are addressed together.
Practice Questions
- 1 A student’s cortisol level is 32 units after a stressful event. If the half-life is 60 minutes and no new cortisol is added, what level remains after 3 hours?
- 2 A person’s resting heart rate is 72 beats per minute. During a month of chronic stress, it rises by 15 percent. What is the new resting heart rate?
- 3 Two people experience the same exam week. One sleeps regularly, exercises, and relaxes after studying, while the other sleeps poorly and worries for days after each exam. Explain which person is more likely to build allostatic load and why.