Stress — Physiology, Causes, and Effects on Health

Stress is the body's response to any demand or threat that is perceived as exceeding a person's resources to cope. Although we often think of it as purely psychological, stress produces a cascade of measurable physiological changes, and understanding these changes is central to explaining how stress damages health. The pioneering account came from Hans Selye, who in the 1930s and 1950s described the General Adaptation Syndrome (GAS). Working with rats exposed to varied harmful conditions, Selye noticed they showed the same pattern of physical response regardless of the specific stressor, leading him to argue that the body reacts to stress in a general, non-specific way through three stages. In the alarm stage, the body detects the threat and mobilizes resources, triggering the fight-or-fli