New! Sign up for our free email newsletter.
Reference Terms
from Wikipedia, the free encyclopedia

Stress (medicine)

Stress is a medical term for a wide range of strong external stimuli, both physiological and psychological, which can cause a physiological response called the general adaptation syndrome. Historically, it was gradually realized that such concepts as anxiety, antagonism, exhaustion, frustration, distress, despair, overwork, pre-menstrual tension, over-focusing, confusion, mourning, and fear could all come together in a general broad term, stress.

The use of the term stress in serious and recognized cases, such as those of post-traumatic stress disorder and psychosomatic illness, has scarcely helped clear analysis of the generalized "stress" phenomenon. Nonetheless, some varieties of stress from negative life events (distress) and from positive life events (eustress) can clearly have a serious physical impact distinct from the troubles of what psychotherapists call the "worried well." Stress activates the sympathetic branch of the autonomous nervous system and the release of stress hormones including epinephrine, and cortisol.

Sympathetic nervous output produces the fight-or-flight response, causing the body to divert bloodflow to large muscles as the body prepares to run away from or fight something. Less blood flows to the digestive system and other organs that do not assist in fleeing or fighting, producing dry mouth, motor agitation, sweating, pallor, enlarged pupils and over the long term, insomnia. Modern stressors can cause continual sympathetic nervous system activation with very little opportunity for the parasympathetic nervous system to activate. When the parasympathetic system is active, the bowel and other non-muscle organs receive good blood-flow, the pupils constrict, and the glands all function well and secrete their various compounds.

Related Stories
 


Mind & Brain News

October 8, 2025

Scientists have discovered that DMT, a natural compound found in plants and even the human brain, can dramatically reduce brain damage caused by stroke. The psychoactive molecule, long known for its hallucinogenic effects, restored the blood-brain ...
Researchers in Japan have pinpointed a biological cause of Long COVID brain fog using advanced PET brain imaging. They discovered widespread increases in AMPA receptor density linked to cognitive ...
Addiction often isn’t about chasing pleasure—it’s about escaping pain. Researchers at Scripps Research have discovered that a tiny brain region called the paraventricular nucleus of the ...
A University of New Mexico scientist is revealing what might be one of the most overlooked causes of dementia — damage in the brain’s tiny blood vessels. Dr. Elaine Bearer has created a new way to classify these changes, showing that many people ...
A new study shows glioblastoma isn’t confined to the brain—it erodes the skull and hijacks the immune system within skull marrow. The cancer opens channels that let inflammatory cells enter the brain, fueling its deadly progression. Even drugs ...
Stanford scientists found that aging disrupts the brain’s internal navigation system in mice, mirroring spatial memory decline in humans. Older mice struggled to recall familiar locations, while a few “super-agers” retained youthful brain ...
Researchers from Leeds found that overeating is driven more by what people believe about food than by its actual ingredients or level of processing. Foods perceived as fatty, sweet, or highly processed were more likely to trigger indulgence. ...
Scientists discovered that lifelong social support can slow biological aging. Using DNA-based “epigenetic clocks,” they found that people with richer, more sustained relationships showed younger biological profiles and lower inflammation. The ...
Researchers have uncovered how a protein called MRAP2 acts as a key regulator of hunger. It helps move the appetite receptor MC4R to the cell’s surface, allowing it to send stronger “stop eating” signals. The discovery offers new hope for ...
A massive new study combining observational and genetic data overturns the long-held belief that light drinking protects the brain. Researchers found that dementia risk rises in direct proportion to alcohol consumption, with no safe level ...
Researchers uncovered a key cellular regulator, PP2A-B55alpha, that controls both the cleanup of damaged mitochondria and the creation of new ones. In Parkinson’s disease models, reducing this regulator improved symptoms and mitochondrial health. ...
New research from Houston Methodist reveals how obesity may directly drive Alzheimer’s disease. Scientists discovered that tiny messengers released by fat tissue, called extracellular vesicles, can carry harmful signals that accelerate the buildup ...

Latest Headlines

updated 12:56 pm ET