What is Allostasis?
Allostasis is the process by which the body maintains stability through physiological change, actively adjusting internal states to meet anticipated demands. Unlike homeostasis (returning to a fixed set point), allostasis involves the brain predicting future needs and proactively adjusting physiology.
How it works
Sterling and Eyer (1988) proposed allostasis to explain how chronic stress damages health: the brain continuously adjusts hormonal, cardiovascular, and immune parameters to prepare for anticipated threats. When threats are chronic, the allostatic adjustments themselves become damaging (allostatic load). Elevated cortisol, increased blood pressure, and suppressed immune function are adaptive short-term responses that cause disease when maintained indefinitely.
Applied example
A person in a chronically stressful job has their HPA axis set to a higher baseline cortisol level (allostatic adjustment). While this keeps them alert and responsive, the sustained elevation damages cardiovascular tissue, disrupts sleep, and impairs immune function, accumulating allostatic load.
Why it matters
Allostasis reframes stress-related disease: the damage comes not from the stressor itself but from the body’s sustained preparatory response, explaining why chronic psychological stress produces physical illness.
