general adaptation syndrome

The general adaptation syndrome is a three-act story of how the body copes with stress that drags on. Proposed by Hans Selye, it describes a predictable arc: a first jolt of alarm, then a long stretch of holding the line, and finally collapse if the strain never lets up. It was the first attempt to describe stress as a single, stereotyped bodily process regardless of the trigger.

The three stages are the alarm reaction, in which the fight-or-flight and HPA systems fire and resistance briefly dips; the stage of resistance, in which the body adapts and sustains high cortisol to cope, appearing outwardly stable; and the stage of exhaustion, in which prolonged demand depletes reserves and defenses fail, opening the door to illness. Selye noticed that very different stressors, cold, injury, toxins, produced a similar pattern of adrenal enlargement and immune shrinkage.

The model is historically pivotal but is now seen as oversimplified. The idea of a literal exhaustion of the adrenals is not well supported, and modern accounts stress that the response is not truly nonspecific. Still, the framework named the concept of stress in physiology and shaped everything that followed.