In 1925 a second year medical student named Hans Selye observed that people suffering from a wide variety of somatic (physical) disorders all seemed to have the same or similar symptoms. For example, many of these people reported: decreased appetite, decreased muscular strength and endurance, and lowered levels of ambition or drive.a psychological and physical response of the body that occurs whenever we must adapt to changing conditions, whether those conditions be real or perceived.
Selye, unable to find a common disease or disorder to explain these behaviours, called this group of symptoms, the SYNDROME OF JUST BEING SICK. In addition, he found that these symptoms occurred whenever: the human organism needed to adapt to a changing internal or external environment.
This was the first observation and identification that eventually led to the term STRESS.
At first, Selye defined STRESS as, a nonspecific response of the body to any demand made upon it. Even this initial definition implies that not all stress is a result of "bad" things happening to us.
Later, his JUST BEING SICK syndrome evolved into the GENERAL ADAPTATION SYNDROME which he defined as, the physiological processes and results of stress.
From this, we get a modern, more comprehensive definition of STRESS:
a psychological and physical response of the body that occurs whenever we must adapt to changing conditions, whether those conditions be real or perceived.