The human body has always been assaulted by stress, but we’ve only recently turned our attention to studying the actual causes and effects of stress in the course of daily life. The body of medical and psychological research devoted to the subject dates back more than seventy years to the 1930s when Dr. Hans Selye, an Austrian-born scientist working at McGill University in Canada, first observed and documented the effects of physical stress on living creatures.
Credited with defining our modern concept of stress, Selye began publishing his first research paper on the topic in 1936. He went on to make the study of stress his life’s work, documenting effects caused by both physical and emotional factors and creating a unified theory of stress, and eventually becoming president of the International Institute of Stress at the University of Montreal.
Selye began his studies by creating physical stress in laboratory rats, first by injecting them with foreign substances or toxins, and noting the changes induced. Over time, he identified a whole system of physiological responses to the challenges he was imposing on his subjects. As his research progressed, Selye learned that other mammals, as well as humans, have similar physical responses to stress. He called these reactions adaptation, and he noted that the long-range impact of stress on bodily systems is essentially the same whether the stress is induced with a toxin, as the result of injury, or is psychological in origin.
A central finding of Selye’s was that a physical stressor or the perception of a threat produces neurochemical and hormonal responses in the body (both elements of the fight-or-flight stress response) will mobilize the body’s resources to deal with the problem. He called this first stage of stress the alarm stage, characterized by such physical changes as quickened heartbeat, rapid breathing, slowed digestion, increased sugar circulating in blood serum, and decreased fat absorption.
The second stage of more prolonged exposure to stress he named the resistance stage. In this stage, the body acclimates to the presence of the stressor and body systems remain in a heightened state of arousal, bringing about their defenses to deal with the threat. If the physical challenge or emotional threat is not adequately met or does not alleviate during the alarm or resistance phase, the body cannot return to a state of relaxation and it remains stressed and a third stage of exhaustion ensues. In this stage, the stress response system goes awry; bodily resources are drained, unable to maintain the high level of readiness. Illness and even death may result if stress persists.