6 ideas
The body's stress response — mobilizing energy, raising heart rate, shutting down digestion and reproduction — is exquisitely adapted for the seconds-long emergency of fleeing a predator. The system malfunctions in humans because we activate the identical physiological cascade for chronic psychological worries that never resolve into physical action.
The stress response itself is not pathological; the disease comes from sustaining it for months or years. Diverting resources from long-term projects like immunity, tissue repair, and digestion is survivable for minutes but corrosive when the alarm never shuts off.
Prolonged stress floods the body with glucocorticoids that actively dismantle immune defenses, killing lymphocytes and shrinking immune tissue. The initial stress-induced immune boost is brief, after which sustained cortisol leaves the organism more vulnerable to infection and slower to heal.
Identical physical stressors produce far less physiological damage when the organism has warning signals, perceived control, an outlet for frustration, and social support. The psychological appraisal of a stressor — not the stressor's objective magnitude — largely determines how harmful it is.
Sustained glucocorticoid exposure damages neurons in the hippocampus, a brain region critical for memory and for shutting off the stress response itself. This creates a feed-forward loop where stress impairs the very structure that would otherwise terminate the stress signal.
In baboon troops, an individual's position in the dominance hierarchy predicts its baseline stress hormone levels, but the relationship depends on the social context — whether the hierarchy is stable, how rank is exercised, and personality. The same biological body experiences vastly different stress loads depending on where it sits socially and how it interprets that position.