Whether animal, vegetable, mineral or machine, everything experiences stress — broadly defined as challenges to equilibrium, a balanced state of being.
The Human Stress Story
In biology, stress is the body’s response to perceived threats to our physical or mental well-being. Moderate amounts are healthy and normal. But too much — or too little — causes problems. Chronic stress is linked to cardiovascular disease, anxiety and depression. Stress associated with extreme events such as combat can lead to post-traumatic stress disorder (PTSD). Symptoms of PTSD, which affects over 7 million Americans, include flashbacks and hypervigilance long after a trauma. Meanwhile, recent studies show that people who underreact to stress are more likely to have impulsive behavior and substance addiction.
The Adaptive Stress Response
A 1936 Nature paper launched the field of stress research. In the study, physician Hans Seyle — later called the father of stress — subjected rats to cold, drugs, excessive exercise and other assaults. Whatever the stimuli, the rats exhibited similar physiological effects.
