stress

Stress is a person's response to a stressor such as an environmental condition or a stimulus. Stress is a body's way to react to a challenge. According to the stressful event, the body's way to respond to stress is by sympathetic nervous system activation which results in the fight-or-flight response. Stress typically describes a negative condition or a positive condition that can have an impact on a person's mental and physical well-being.

The term stress had none of its contemporary connotations before the 1920s. It is a form of the Middle English destresse, derived via Old French from the Latin stringere, "to draw tight. The word had long been in use in physics to refer to the internal distribution of a force exerted on a material body, resulting in strain. In the 1920s and 1930s biological and psychological circles occasionally used the term to refer to a mental strain or to a harmful environmental agent that could cause illness. Walter Cannon used it in 1926 to refer to external factors that disrupted what he called homeostasis. But "[...] Stress as an explanation of lived experience is absent from both lay and expert life narratives before the 1930s".

Homeostasis is a concept central to the idea of stress. In biology, most biochemical processes strive to maintain equilibrium, a steady state that exists more as an ideal and less as an achievable condition. Environmental factors, internal or external stimuli, continually disrupt homeostasis; an organism’s present condition is a state in constant flux moving about a homeostatic point that is that organism’s optimal condition for living. Factors causing an organism’s condition to diverge too far from homeostasis can be experienced as stress. A life-threatening situation such as a physical insult or prolonged starvation can greatly disrupt homeostasis. On the other hand, an organism’s effortful attempt at restoring conditions back to or near homeostasis, often consuming energy and natural resources, can also be interpreted as stress. In such instances, an organism’s fight-or-flight response recruits the body's energy stores and focuses attention to overcome the challenge at hand.

The ambiguity in defining this phenomenon was first recognized by Hans Selye (1907-1982) in 1926. In 1951 a commentator loosely summarized Selye's view of stress as something that "…in addition to being itself, was also the cause of itself, and the result of itself. First to use the term in a biological context, Selye continued to define stress as "the non-specific response of the body to any demand placed upon it". As of 2011 neuroscientists such as Bruce McEwen and Jaap Koolhaas believe that stress, based on years of empirical research, "should be restricted to conditions where an environmental demand exceeds the natural regulatory capacity of an organism".Despite the numerous definitions given to stress, homeostasis appears to lie at its core.