Hans SelyeHans Selye (1907 - 1982) was an Austrian physician who did much important theoretical work on the physical effects of stress. He is considered to have been the first to demonstrate the existence of a separate stress disease, the stress syndrome, or General adaptation syndrome.
To grossly oversimplify, Selye discovered and documented that stress differs from other physical responses in that stress is stressful whether the news is good or bad, whether the impulse is positive or negative. He called negative stress distress and positive stress eustress.
Selye is said to have discovered the stress syndrome when in medical school he observed that people who had various illnesses seemed to share a quality of "sickness" that was highly similar.