Stress and General Adaptation Syndrome

6 min read Updated Apr 19, 2026

Stress is the bodily and psychological response to demands that challenge or threaten the organism. This section covers what counts as stress, how the body responds, and how prolonged stress changes physiology and behavior.

What Is Stress? Lazarus’s Appraisal Model

Richard Lazarus - whom you met among the theories of emotion - argued that stress depends less on the objective event and more on your appraisal of it.

Primary appraisal. Is this event irrelevant, benign/positive, or stressful/negative? If benign, no stress response. If stressful, move to secondary appraisal.
Secondary appraisal. Can I cope with it? Evaluate harm (damage already done), threat (damage still to come), and challenge (can I overcome it?). Your coping resources matter as much as the objective threat.

Two people facing the same deadline may appraise it completely differently: one as a fun challenge, one as a terrifying overload. Appraisal creates the stress.

Vertical flow chart of Lazarus's transactional stress model: environmental stressors pass through a perception filter to a person; primary appraisal categorizes the stimulus as positive, dangerous, or irrelevant; secondary appraisal evaluates resources as sufficient or insufficient; resulting stress triggers problem-focused or emotion-focused coping, leading to reappraisal — Lazarus's transactional model of stress and coping. A stressor only becomes "stress" after primary appraisal flags it as dangerous and secondary appraisal finds resources insufficient. Coping strategies feed back through reappraisal - the model that anchors most MCAT stress passages. *Credit: Philipp Guttmann via Wikimedia Commons (CC BY-SA 4.0).*

Four Categories of Stressors

Significant life changes - marriage, death of a loved one, new job, divorce. Even positive changes are stressful.
Catastrophic events - large-scale threats, natural disasters, war, pandemics.
Daily hassles - small repeated irritations: traffic, email, misplaced keys, interpersonal friction. Often linked to low socioeconomic status (unemployment, inadequate income). Research suggests daily hassles may be the most important stressor for overall health because of their chronicity.
Ambient stressors - environmental conditions you don’t control: noise, pollution, crowding. Often below conscious awareness but measurably stressful.

The Acute Stress Response

Walter Cannon described the fight-or-flight response - the sympathetic nervous system’s rapid mobilization for threat. Two integrated arms:

Sympathetic Nervous System

Fast neural signals cause:

Increased heart rate and respiration (more O₂ to muscles)
Peripheral vasoconstriction (blood shunted to vital organs)
Pupil dilation, decreased salivation
Digestion, immune function, and reproduction temporarily suppressed
Release of epinephrine and norepinephrine from the adrenal medulla

Endocrine Response (HPA Axis)

Slower hormonal signals route through the hypothalamus-pituitary-adrenal axis:

Hypothalamus → CRH → anterior pituitary
Pituitary → ACTH → adrenal cortex
Adrenal cortex → cortisol (a glucocorticoid)

Cortisol mobilizes glucose (raises blood sugar), suppresses the immune system, and redirects energy to immediate needs. Mnemonic: COrtisol is released by the CORTex.

Flow diagram of the HPA axis showing the hypothalamus releasing CRH to the anterior pituitary, the pituitary releasing ACTH to the adrenal cortex, and the adrenal cortex releasing cortisol, with cortisol exerting negative feedback on both the hypothalamus and pituitary — The HPA (hypothalamic-pituitary-adrenal) axis. CRH from the hypothalamus drives ACTH release from the anterior pituitary, which triggers cortisol release from the adrenal cortex. Cortisol then loops back to inhibit the upstream signals - a classic negative-feedback endocrine cascade. *Credit: Biolinkage Project via Wikimedia Commons (CC BY-SA 4.0).*

Anatomy diagram showing an adrenal gland sitting atop a kidney, zoomed to a histology view of the cortex layers (zona glomerulosa, fasciculata, reticularis) and medulla, with each layer paired to its hormone class: mineralocorticoids (aldosterone), glucocorticoids (cortisol, cortisone), androgens (DHEA), and stress hormones (epinephrine, norepinephrine) — The adrenal gland in cross-section. The cortex (outer) releases cortisol from the zona fasciculata under HPA-axis control; the medulla (inner) releases epinephrine and norepinephrine under sympathetic neural control. Two anatomically and functionally distinct stress arms in one organ. *Credit: OpenStax College via Wikimedia Commons (CC BY 3.0).*

Tend-and-Befriend Response

Not everyone responds to stress with fight or flight. Tend and befriend is an alternative response, more common in women, characterized by seeking social support and caring for offspring. Driven partly by oxytocin (a bonding hormone linked to estrogen), it moderates the classic sympathetic response and favors affiliative behavior over aggression.

General Adaptation Syndrome (GAS)

Hans Selye proposed that prolonged stress unfolds in three phases:

Three-phase line graph of resistance to stress over time, with the curve starting at baseline, dipping briefly during the yellow Alarm phase, climbing to a peak during the orange Resistance phase, then crashing well below baseline in the gray Exhaustion phase — Hans Selye's General Adaptation Syndrome. After an initial dip during alarm, resistance climbs and stays elevated as the body fights the stressor; once resources deplete, exhaustion drops resistance below baseline - the zone where chronic stress causes disease. *Credit: David G. Myers, Exploring Psychology, via Wikimedia Commons (CC BY 3.0).*

Phase 1: Alarm

Immediate stress reaction. Heart races, HPA axis kicks in, resources mobilized. “Ready for fight or flight.”

Phase 2: Resistance

The body adjusts to maintain function under continuing stress. Cortisol stays elevated, blood pressure high, breathing rapid. Short-term the body copes; long-term this is unsustainable.

Phase 3: Exhaustion

If the stressor doesn’t resolve, resources deplete. Tissues are damaged. Immunity drops. This is where chronic stress produces real disease: hypertension, heart disease, immunosuppression, metabolic problems, depression.

What is the difference between primary and secondary appraisal in Lazarus's stress theory?

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Primary appraisal: is the event stressful or not? Secondary appraisal: if stressful, can I cope? Evaluates harm, threat, and challenge. Both stages together determine the stress response.

What hormone does the adrenal cortex release during stress, and what are its main effects?

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Cortisol (a glucocorticoid). Mobilizes glucose, suppresses immunity, and redirects energy to immediate needs. Chronic elevation is implicated in cardiovascular, metabolic, and mental health problems.

List Selye's three phases of general adaptation syndrome and briefly describe each.

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Alarm (immediate fight-or-flight mobilization), Resistance (sustained coping with continuing stress), Exhaustion (resources depleted, tissues damaged, disease emerges). ARE.