An update on physiological effects of stress

The awareness of stress was increased after World War II when it was noticed that many routine life events like examinations, growing up increases stress and leads to dysfunction.1 The word stress was used by Hans Selye for the first time in 1936 to explain the effects of threats that disturbs homeostasis.2,3 Walter B. Cannon explained the role of adrenal glands and sympathetic nervous system in maintenance of body equilibrium after exposure to threat. Hans Selye3 defined stress as a set of non-specific responses collectively called as “General Adaptation Syndrome”. Hans Selye’s theory of non-specificity was criticized by Mason4 Goldstein5 defined stress as “stress is a condition in which expectations, whether genetically programmed, established by prior learning or deduced from circumstances, do not match the current or anticipated perceptions of the internal or external environment and this discrepancy between what is observed or sensed and what is expected or programmed elicits patterned, compensatory responses”. Later the word allostasis was introduced to stress research, which is the process of adaptation to different stressors. When there is any defect in the process of adaptation, it leads to “allostatic load or overload”.6 Stress may be acute or episodic acute or chronic stress, which varies in characteristics, symptoms, duration and management approaches. The most commonly experienced stress is acute stress. Emotional distress, muscular, gastro intestinal problems, hypertension, tachycardia, decrease in the respiratory rate are symptoms of acute stress. Episodic acute stress is more common in people who regularly experience acute stress. Prolonged depression, anxiety and distress, coronary heart disease is most common symptoms of episodic acute stress. Long term exposure to stressor leads to chronic stress. Chronic stress is hazardous as it increases suicidal tendency. As acute stress is short-term, people are aware of it, but they may be unaware of chronic stress.7 Stress has both positive and negative impact. Up to a limited level of threshold, stress may be beneficial. However, beyond this level, there will be sharp fall in the productivity. Hence, one should be aware of the indicators of stress. Common indicators of stress are irritability, insomnia, anxiety and/or feeling of giving up. However, the peak level of stress and indicators of stress varies from person to person. Considering these facts, Hans Selye3 stated that ‘eustress’ or ‘good stress’ increases productivity and ‘distress’ or ‘bad stress’ decreases the productivity. Eustress is required as it helps to complete a task; in contrast, distress may lead to depression. The current article reviews the effect of stress on different body systems. Physiological effects of stress