**3. Stress**

Claude Bernard noted that the maintenance of life is critically dependent on keeping our internal milieu constant in the face of a changing environment. In 1956, Selye coined the term "stress" to represent the effects of anything that seriously threatens homeostasis. The actual or perceived threat to an organism is referred to as the "stressor" and the response to the stressor is called the "stress response." Although stress responses evolved as adaptive processes, Selye observed that severe, prolonged stress responses might lead to tissue damage and disease. During pandemics, the victims and at-risk groups tend to experience stress. As a consequence of the pandemic, even the health professionals who were overworked suffered high level of psychophysical stress. Various tools and questionnaires have been devised to measure stress levels in individuals. The most commonly used are DASS-21 and SAS. Studies have shown that psychological stress can affect the immune system through neuroendocrine pathways [14].
