Stress

DEFINITION: A psychophysiological response to real or perceived pressures in the environment, including danger; prolonged stress contributes to hormonal imbalances, lowered immune system function, and increased susceptibility to disease, cancer, and death.

ANATOMY OR SYSTEM AFFECTED: All

Causes and Symptoms

Stress is a psychophysiological response to a real or perceived danger. Stress involves a complex interplay of nervous and hormonal reactions to internal and external stimuli. All living organisms respond to stimuli, usually by means of gene-regulating chemical messengers called hormones.

Chemistry of stress. Hormones are produced in certain cells and then target tissues elsewhere in the body; these hormones can affect changes in gene expression. Hormones will activate certain genes within target tissue cells while inactivating other genes. If a hormone activates the control region of a gene so that the gene is “on,” then it can be “read” by an enzyme (RNA polymerase), thereby leading to RNA and protein production. The produced protein may affect cellular chemical processes or may affect the expression (the on/off status) of other genes. In the latter case, the protein would be a type of intracellular hormone called an alarmone.

If a hormone inactivates the control region of a gene so that the gene is “off,” then RNA polymerase will be unable to read the DNA nucleotide sequence of the gene. Therefore, no RNA and no protein will be produced. In this fashion, a hormone may activate certain genes while inactivating others. Consequently, a hormone controls what happens within the cell.

The body is regulated by hormones and by complex nervous systems that evolved from hormones. Most hormones are produced and secreted from the glands of the endocrine system, including the pituitary, thyroid, and adrenal glands, as well as numerous organs, tissues, and cells throughout the body. The nervous system is an array of several trillion nerves concentrated in the brain and spinal cord and extending peripherally to virtually every cellular region of the body. The two systems are tightly interconnected. Both the endocrine and nervous systems, at some point, involve the secretion of hormones. Nerve tissue secretes hormones called neurotransmitters between electrically conducting cells called neurons.

Physiological responses to stress. Stress is, therefore, a biochemical response to danger that occurs within animals. The nervous system detects danger from internal or external stimuli, usually external stimuli, such as predators, competitors, or life-threatening events. Increased electrical conductivity along millions of nerve cells targets various tissues to prepare the body for maximum physical activity. Among the tissues affected will be the skeletal muscles, the heart muscle, the hormone-secreting glands of the endocrine system, the immune system, the stomach, and blood vessels. Under nerve-activated stress, skeletal muscles will be poised for contraction. The heart will beat faster, thereby distributing more blood and nutrients to body cells, in the process accelerating the breathing rate to distribute more oxygen. Blood vessels will constrict. The stomach and other intestinal organs will decrease their activity, including a decreased production of mucus that protects against acid.

Heightened nerve activity also will trigger the production of various hormones from the immune system, specifically hormones that influence bodily metabolism, such as thyroxine and epinephrine (adrenaline). These hormones target body tissue cells to prepare the body for increased output in the face of danger. Massive production of epinephrine will trigger maximum physical readiness and extraordinary muscular output, a phenomenon often referred to as the fight-or-flight response.

These physiological changes within an animal facing danger are important survival adaptations that evolved very early in the history of animal life on Earth. Competition for available food resources and avoidance of predators must be faced by all animals, including humans. While predation by larger animals is of little worry to modern humans, the struggle for available resources remains. Furthermore, human technology has created stresses of an entirely different character.

The fight-or-flight stress response and other evolutionary stress adaptations are excellent for moments of acute stress that endure within the individual for only a few seconds or minutes. The stresses that humans face are based on these behavioral adaptations. Much of the stress faced by modern-day humans is chronic, however, and lasts not for minutes but for hours, days, weeks, months, and years. Such stresses involve the same nervous and endocrine system responses, but they are usually brought about by perceived danger, not true danger. Further, because the stress is not resolved within the immediate outcome of a situation and is felt chronically, humans often suffer a prolonged stress response that may interfere with modern daily life.

Human societies impose norms and rules for the behavior of the individuals who compose the society. People must adhere to the societal norms or face punishment. In fast-paced technological societies, increasing bureaucratization and organization place less emphasis on the individual and more emphasis on process and productivity. People face deadlines, produce quotas, generate company profit, and meet the demands of family, colleagues, and administration simultaneously. Through social media, people feel pressured to appear a certain way or respond to a constant barrage of comments and messages. The result is a continuous fight-or-flight response in which individuals fear losing their jobs or their relationships and, thus, the means of supporting themselves and their families and being ostracized from their social circles.

The physiological manifestations of prolonged stress are devastating. Continued hyperactivity of nerve impulses and overproduction of hormones at incorrect developmental stages lead to the abnormal functioning of internal organs. The stomach undersecretes mucus, thereby leading to ulcers. The heart muscle contracts too rapidly, leading to higher pulse and respiration rates. The blood vessels constrict for lengthy periods of time, thereby causing the heart to pump harder and leading to high blood pressure and heart disease. Hormone overproduction leads to incorrect cell instructions and gene activation/inactivation, causing abnormal tissue functioning and cellular transformation leading to cancer. The immune system weakens under abnormal signaling by hormones, thereby decreasing the body’s ability to defend itself from disease.

Newer research on stress response in women has uncovered a mechanism of stress response that is of interest given this upswelling of constant stress. Work by Shelley E. Taylor has documented an alternative to “fight or flight” known as “tend and befriend.” Potentially linked to oxytocin, such tend-and-befriend behavior may help to facilitate relaxation and interpersonal bonding in response to stress. The potential stress response promises longer-lasting benefits, adaptively connecting humans to their social groups.

Stress and disease. A wide variety of human illnesses and disorders have been associated with stress. Heart disease, certain cancers, stroke, mental illness, allergies, accidents, asthma, chronic fatigue, chronic pain, and suicide are among the many illnesses and disorders that are considered by scientists to be stress-related illnesses. Six of the top ten leading causes of death in the United States, including heart disease, cancer, respiratory diseases, unintentional injuries (accidents), stroke, and suicide, are linked to chronic stress. Some studies have estimated that the majority of all visits to primary care physicians are due to stress-related complaints, such as headaches, muscle tension, peptic ulcers, chronic pain, lowered immune system function, and flare-ups of rheumatoid arthritis and systemic lupus erythematosus.

There still is some debate concerning the causal relationship between stress and illness, despite overwhelming scientific evidence demonstrating bodily responses to stressful situations. Abnormal nerve hyperactivity and prolonged, abnormal secretions of gene-regulatory hormones from various endocrine glands disrupt the balanced homeostasis of many different body systems. Immune system reduction often occurs due to chronic stress, thereby making a stressed individual more susceptible to contracting infectious bacterial and viral diseases.

A clear link exists between the occurrence of stress in people and their subsequent susceptibility to infectious disease. Furthermore, there is a tendency for strokes, heart attacks, cancer, and sudden death to occur in individuals who have recently experienced major traumatic events. Too little attention has been given to the effects of everyday living on the physical well-being of people. Environmental stimuli, nervous and endocrine systems, and physiological rhythms within the body are intricately connected.

Most bodily processes follow a self-regulatory, homeostatic pattern that is rhythmic, linear, stable, and predictable. For example, the beta cells of the islets of Langerhans in the pancreas secrete the hormone insulin in response to elevated blood glucose levels, whereas the alpha cells in these same islets secrete the hormone glucagon in response to low blood glucose levels. Likewise, the body chemically maintains a constant blood temperature (37 degrees Celsius), pH (7.35 to 7.45), calcium levels, and so on. The heart muscle requires an electrical stimulus approximately once per second to trigger a wave of muscular contractions throughout the myocardium via the sinoatrial and atrioventricular nodes.

Linear, balanced physiological rhythms are sensitive to subtle chemical changes in the cellular and organismal environment. Stress is a disturbance that imbalances the nervous and endocrine systems, which subsequently imbalance cells and organ systems throughout the human body. Physiological systems become unstable, and disease may ensue.

Treatment and Therapy

Psychologists, psychiatrists, physicians, and other medical professionals are becoming more aware of the physiological effects of stress. Through this awareness, medical professionals sought to examine whether there are any characteristic styles of stress response. In response, psychologists identified two principle behavioral types when it comes to stress among humans: type A behavior pattern and type B behavior pattern. Type A individuals are anxious, task-oriented, time-conscious, constantly in a rush to accomplish their jobs and other objectives, and somewhat prone to hostility. Research indicates that type A individuals may have a higher incidence of heart disease. Increasingly, the hostility component of type A behavior is seen as a very important contributing factor. On the other hand, type B individuals are more relaxed and experience less stress. Nevertheless, it should be emphasized that behavior is a continuum: different people may exhibit varying degrees of type A and B behavior patterns. Given this discovery, it is not uncommon for professionals to recommend to their stressed clients to monitor their participation in type A behavior and to try behaving more in kind with type B behavior patterns.

Another important focus for healthcare has become the prevention, management, and treatment of stress itself. Health education programs emphasize the importance of physical fitness and stress reduction techniques in everyday living. Stress-reducing techniques include time management training, meditation emphasizing mindfulness, yoga, physical activity, peer counseling and support, spending longer amounts of time relaxing, strengthening social bonds, improving self-esteem, and learning to reframe how daily life events are interpreted, such as may be done through cognitive behavioral therapy. These approaches greatly enhance an individual’s quality of life and help the individual to cope positively with stressful events. All these stress reduction techniques emphasize an individual’s personality and the more efficient use of an individual’s free time. Relaxation, social interaction, and physical activity help the body to return to normal physiological rhythms following the numerous stressful events that every person faces daily. Many individuals are coming to realize that a slower, more relaxed living pace is helpful for reducing stress and the millions of cases of stress-related disease that occur each year.

Perspective and Prospects

Because stress is a major contributor to illness and disease, a major objective of healthcare professionals is the identification of stress initiators and the reduction of stress in the general population. Stress cannot be eliminated entirely in any individual. Humans always will experience stress as a result of their continuous interactions with one another and with the environment. Stress is an important survival adaptation for animal life on Earth. Nevertheless, stressful events in an individual’s life serve as negative environmental stimuli that hyperactivate the human nervous and endocrine systems to create a fight-or-flight response. When this fight-or-flight response is maintained for abnormally long periods of time, prolonged elevations in nervous and hormonal activity modify body tissues and the developmental gene expression within cells to lead to abnormal system functioning. The net result of physiological stress is illness, disease, pain, rapid aging, and death. Further, life is full of unpredictable and life-altering events. These may be personal in nature or they may affect the whole of society as seen in the coronavirus disease 2019 (COVID-19) pandemic of the 2020s. Though some groups, such as healthcare personnel were disproportionately affected, the pandemic raised stress levels for almost all individuals dealing with the disease which hastened the physical manifestations of the virus.

Stress reduction is a prime focus of medical research and education. The simplicity of educating the public with respect to stress can yield incredible savings in terms of lives saved, quality of lives improved, length of human life spans increased, and money saved. Some researchers propose that stress reduction not only can yield enormous health benefits but also can produce greater industrial productivity, happier people, and considerably less crime. It is expected that additional research into oxytocin, the tend-and-befriend response, and yet undiscovered mechanisms of stress response will contribute meaningfully to decreased stress and increased mental and physical well-being.

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