Linas A Bieliauskas 
Stress And Its Relationship To Health And Illness [PDF ebook] 

To discuss the relationship between stress and health status, it is first necessary to define the term "stress." This is not a mundane issue, because the term "stress" is popularly used to refer to a wide range of physiological changes, psychological states, and environmental pressures in the health/illness literature. Stress was first described as a biological syndrome by Selye (1936, p. 32): Experiments on rats show that if the organism is severely damaged by acute non-specific nocuous agents such as exposure to cold, surgical injury, production of spinal shock … a typical syndrome appears, the symptoms of which are independent of the nature of the damaging agent … and represent rather a response to damage as such.