This article is about the concept of "stress" in relation to biology. . For the concept of "stress" in physics and mechanics, see Stress_(mechanics).
Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance. It refers to the consequence of the failure of an organism — human or other animal — to respond adequately to mental, emotional, or physical demands, whether actual or imagined.
Signs of stress may be cognitive, emotional, physical, or behavioral. Signs include poor judgment, a general negative outlook, excessive worrying, moodiness, irritability, agitation, inability to relax, feeling lonely, isolated or depressed, acne, aches and pains, diarrhea or constipation, nausea, dizziness, chest pain, rapid heartbeat, eating too much or not enough, sleeping too much or not enough, social withdrawal, procrastination or neglect of responsibilities, increased alcohol, nicotine or drug consumption, and nervous habits such as pacing about, nail-biting, and neck pains.