In contrast to the common interpretation of the term "stress" as a psychological phenomenon, it should be understood as any real or perceived disturbance of an organism's homeostasis, or state of harmony or balance. For example, in this viewpoint a severe hemorrhage, starvation, extreme temperature, or worry about the unpredictable onset of abdominal pain all qualify as stressors – some as "physical" stressors, others as "psychological" stressors. The fear to leave the house in the morning without knowing if one can make it to work without having to stop on a busy highway because of an uncontrollable bowel movement, or the fear of experiencing uncontrollable abdominal discomfort during an important business meeting are sufficient stressors to activate the central stress system."
The Neurobiology of Stress and Emotions
By: Emeran A. Mayer, M.D.UCLA Collaborative Centers for Integrative Medicine, UCLA School of Medicine, California
We often hear the term "stress" associated with functional gastrointestinal (GI) disorders, such as irritable bowel syndrome (IBS). Many patients experience a worsening of symptoms during times of severely stressful life events. But what is stress? How often does it occur? How does our body respond to stress? This article explores the mechanisms that link stress and emotions to responses that have evolved to ensure survival and that, in the modern world, affect health—including gastrointestinal function.