Disease risk is particularly pertinent to mental illnesses, whereby chronic or severe stress remains a common risk factor for severalmental illnesses.[1][5]
Acute stressful situations where the stress experienced is severe is a cause of change psychologically to the detriment of the well-being of the individual, such that symptomaticderealization anddepersonalization, and anxiety andhyperarousal, are experienced.[6] TheInternational Classification of Diseases includes a group ofmental andbehavioraldisorders which have theiraetiology in reaction to severe stress and the consequent adaptive response.[7][8] Chronic stress, and a lack of coping resources available, or used by an individual, can often lead to the development of psychological issues such asdelusions,[9]depression andanxiety.[4]
Chronic stressors may not be as intense as acute stressors such as natural disaster or a major accident, but persist over longer periods of time and tend to have a more negative effect on health because they are sustained and thus require the body's physiological response to occur daily.[4] This depletes the body's energy more quickly and usually occurs over long periods of time, especially when these microstressors cannot be avoided.[4]
When humans are under chronic stress, permanent changes in their physiological, emotional, and behavioral responses may occur.[10] Chronic stress can include events such as caring for a spouse with dementia, or may result from brief focal events that have long term effects, such as experiencing a sexual assault. Studies have also shown that psychological stress may directly contribute to the disproportionately high rates ofcoronary heart diseasemorbidity andmortality and its etiologicrisk factors. Specifically, acute and chronic stress have been shown to raiseserum lipids and are associated with clinical coronary events.[11]
However, it is possible for individuals to exhibithardiness—a term referring to the ability to be both chronically stressed and healthy.[12] Even though psychological stress is often connected with illness or disease, most healthy individuals can still remain disease-free after being confronted with chronic stressful events. This suggests that there are individual differences in vulnerability to the potential pathogenic effects of stress; individual differences in vulnerability arise due to both genetic and psychological factors. In addition, the age at which the stress is experienced can dictate its effect on health. Research suggests chronic stress at a young age can have lifelong effects on the biological, psychological, and behavioral responses to stress later in life.[13]
The term "stress" had none of its contemporary connotations before the 1920s. It is a form of theMiddle Englishdestresse, derived viaOld French from theLatinstringere, "to draw tight".[14] The word had long been in use inphysics to refer to the internal distribution of a force exerted on a material body, resulting instrain. In the 1920s and '30s, biological and psychological circles occasionally used "stress" to refer to a physiological or environmental perturbation that could cause physiological and mental "strain". The amount of strain in reaction to stress depends on theresilience. Excessive strain would appear as illness.[15][16]
Walter Cannon used it in 1926 to refer to external factors that disrupted what he calledhomeostasis.[17] But "...stress as an explanation of lived experience is absent from both lay and expert life narratives before the 1930s".[18] Physiological stress represents a wide range of physical responses that occur as a direct effect of a stressor causing an upset in the homeostasis of the body. Upon immediate disruption of either psychological or physical equilibrium the body responds by stimulating thenervous,endocrine, andimmune systems. The reaction of these systems causes a number of physical changes that have both short- and long-term effects on the body.[19]
TheHolmes and Rahe stress scale was developed as a method of assessing the risk of disease from life changes.[20] The scale lists both positive and negative changes that elicit stress. These include things such as a major holiday or marriage, or death of a spouse and firing from a job.[citation needed]
Homeostasis is a concept central to the idea of stress.[21] Inbiology, mostbiochemical processes strive to maintain equilibrium (homeostasis), a steady state that exists more as an ideal and less as an achievable condition. Environmental factors, internal or external stimuli, continually disrupt homeostasis; an organism's present condition is a state of constant flux moving about a homeostatic point that is that organism's optimal condition for living.[22] Factors causing an organism's condition to diverge too far from homeostasis can be experienced as stress. A life-threatening situation such as amajor physical trauma or prolongedstarvation can greatly disrupt homeostasis. On the other hand, an organism's attempt at restoring conditions back to or near homeostasis, often consumingenergy and natural resources, can also be interpreted as stress.[23]
The ambiguity in defining this phenomenon was first recognized byHans Selye (1907–1982) in 1926. In 1951 a commentator loosely summarized Selye's view of stress as something that "...in addition to being itself, was also the cause of itself, and the result of itself".[24][25]
First to use the term in a biological context, Selye continued to define stress as "the non-specific response of the body to any demand placed upon it". Neuroscientists such asBruce McEwen and Jaap Koolhaas believe that stress, based on years of empirical research, "should be restricted to conditions where an environmental demand exceeds the natural regulatory capacity of an organism".[26] Indeed, in 1995 Toates already defined stress as a "chronic state that arises only when defense mechanisms are either being chronically stretched or are actually failing,"[27] while according to Ursin (1988) stress results from an inconsistency between expected events ("set value") and perceived events ("actual value") that cannot be resolved satisfactorily,[28] which also puts stress into the broader context ofcognitive-consistency theory.[29]
The brain endocrine interactions are relevant in the translation of stress into physiological and psychological changes.[4] Theautonomic nervous system (ANS) plays an important role by translating stress reflexively into a response both to physical stressors and higher level inputs by the brain.[30]
The activity of the sympathetic nervous system drives what is called the "fight or flight" response.[4] The fight or flight response to emergency or stress involves increased heart rate and force contraction,vasoconstriction,bronchodilation,sweating, and secretion of the epinephrine and cortisol from theadrenal medulla, among numerous other physiological and hormonal responses.[30] The parasympathetic nervous response involves return to maintaining homeostasis, and involvesmiosis,bronchoconstriction, increased activity of the digestive system, and contraction of the bladder walls.[30] Complex relationships between protective and vulnerability factors on the effect of childhood home stress on psychological illness, cardiovascular illness and adaption have been observed.[4][32] ANS related mechanisms may increase the risk of cardiovascular disease after major stressful events.[4][33]
TheHPA axis is a neuroendocrine system that mediates a stress response.[4] Neurons in the hypothalamus, particularly theparaventricular nucleus, releasevasopressin andcorticotropin releasing hormone, which travel through the hypophysial portal vessel where they travel to and bind to thecorticotropin-releasing hormone receptor on theanterior pituitary gland.[4][30] Multiple CRH peptides have been identified, and their corresponding receptors exist in multiple brain regions, including the amygdala.[4] CRH is the main regulatory molecule of the release of ACTH.[4] The secretion of ACTH into the systemic circulation allows it to bind to and activatemelanocortin receptors, where it stimulates the release ofsteroid hormones.[4] Theimmune system may be influenced by stress. The HPA axis ultimately results in the release of cortisol, which generally has immunosuppressive effects.[4]
Chronic stress is a term sometimes used to differentiate it from acute stress. Definitions differ, and may be along the lines of continual activation of the stress response,[34] stress that causes anallostatic shift in bodily functions,[3] or just as "prolonged stress".[35] While responses to acute stressors typically do not impose a health burden on young, healthy individuals, chronic stress in older or unhealthy individuals may have long-term effects that are detrimental to health.[36]
Some studies have observed increased risk ofupper respiratory tract infection during chronic life stress. In patients with HIV, increased life stress and cortisol was associated with poorer progression of HIV.[34] Also with an increased level of stress, studies have proven evidence that it can reactivate latent herpes viruses.[37]
Chronic stress has also been shown to impairdevelopmental growth in children by lowering thepituitary gland's production of growth hormone, as in children associated with a home environment involving serious marital discord,alcoholism, orchild abuse.[38] More generally, prenatal life, infancy, childhood, and adolescence are critical periods in which the vulnerability to stressors is particularly high.[39][40]
Stressors that are enjoyable or inspiring are termedeustress, which has generally positive effects on energy, cardiovascular health, andcognitive functions.[4]
In 1975, Selye published a model dividing stress intoeustress anddistress.[46] Where stress enhances function (physical or mental, such as throughstrength training or challenging work), it may be considered eustress.[4] Persistent stress that is not resolved through coping or adaptation, deemed distress, may lead toanxiety or withdrawal (depression) behavior.[4][46]
The difference between experiences that result ineustress and those that result indistress is determined by the disparity between an experience (real or imagined) and personal expectations, and resources to cope with the stress.[4][47]
Lazarus[48] argued that, in order for a psychosocial situation to be stressful, it must be appraised as such. He argued that cognitive processes of appraisal are central in determining whether a situation is potentially threatening, constitutes a harm/loss or a challenge, or is benign.
Both personal and environmental factors influence this primary appraisal, which then triggers the selection of coping processes. Problem-focused coping is directed at managing the problem, whereas emotion-focused coping processes are directed at managing the negative emotions. Secondary appraisal refers to the evaluation of the resources available to cope with the problem, and may alter the primary appraisal.
In other words, primary appraisal includes the perception of how stressful the problem is and the secondary appraisal of estimating whether one has more than or less than adequate resources to deal with the problem that affects the overall appraisal of stressfulness. Further, coping is flexible in that, in general, the individual examines the effectiveness of the coping on the situation; if it is not having the desired effect, they will, in general, try different strategies.[49]
Both negative and positive stressors can lead to stress. The intensity and duration of stress changes depending on the circumstances and emotional condition of the person with it (Arnold. E and Boggs. K. 2007). Some common categories and examples of stressors include:
Sensory input such aspain,bright light, noise, temperatures, or environmental issues such as a lack of control over environmental circumstances, such asfood, air and/or water quality,housing,health,freedom, or mobility.
Adverse experiences duringdevelopment (e.g. prenatal exposure to maternal stress,[51][52] poor attachment histories,[53]sexual abuse)[54] are thought to contribute to deficits in the maturity of an individual's stress response systems. One evaluation of the different stresses in people's lives is theHolmes and Rahe stress scale.
Physiologists define stress as how the body reacts to a stressor - a stimulus, real or imagined. Acute stressors affect an organism in the short term; chronic stressors over the longer term. The general adaptation syndrome (GAS), developed by Hans Selye, is a profile of how organisms respond to stress; GAS is characterized by three phases: a nonspecific alarm mobilization phase, which promotes sympathetic nervous system activity; a resistance phase, during which the organism makes efforts to cope with the threat; and an exhaustion phase, which occurs if the organism fails to overcome the threat and depletes its physiological resources.[55]
Antishock phase: When the threat or stressor is identified or realized, the body starts to respond and is in a state of alarm. During this stage, thelocus coeruleus and sympathetic nervous system activate the production of catecholamines including adrenaline, engaging the popularly-knownfight-or-flight response. Adrenaline temporarily provides increasedmuscular tonus, increased blood pressure due toperipheral vasoconstriction andtachycardia, and increased glucose in blood. There is also some activation of theHPA axis, producing glucocorticoids (cortisol, aka the S-hormone or stress-hormone).
Resistance is the second stage. During this stage, increased secretion ofglucocorticoids intensifies the body's systemic response. Glucocorticoids can increase the concentration of glucose, fat, and amino acid in blood. In high doses, one glucocorticoid,cortisol, begins to act similarly to amineralocorticoid (aldosterone) and brings the body to a state similar tohyperaldosteronism. If the stressor persists, it becomes necessary to attempt some means of coping with the stress. The body attempts to respond to stressful stimuli, but after prolonged activation, the body's chemical resources will be gradually depleted, leading to the final stage.
The current usage of the wordstress arose out ofHans Selye's 1930s experiments. He started to use the term to refer not just to the agent but to the state of the organism as it responded and adapted to the environment. His theories of a universal non-specific stress response attracted great interest and contention in academicphysiology and he undertook extensive research programs and publication efforts.[57]
While the work attracted continued support from advocates ofpsychosomatic medicine, many in experimental physiology concluded that his concepts were too vague and unmeasurable. During the 1950s, Selye turned away from the laboratory to promote his concept through popular books and lecture tours. He wrote for both non-academic physicians and, in an international bestseller entitledStress of Life, for the general public.
A broadbiopsychosocial concept of stress and adaptation offered the promise of helping everyone achieve health and happiness by successfully responding to changing global challenges and the problems of moderncivilization. Selye coined the term "eustress" for positive stress, by contrast todistress. He argued that all people have a natural urge and need to work for their own benefit, a message that found favor with industrialists and governments.[57] He also coined the termstressor to refer to the causative event or stimulus, as opposed to the resulting state of stress.
Selye was in contact with thetobacco industry from 1958 and they were undeclared allies inlitigation and the promotion of the concept of stress, clouding the link betweensmoking and cancer, and portraying smoking as a "diversion", or in Selye's concept a "deviation", from environmental stress.[58]
From the late 1960s, academicpsychologists started to adopt Selye's concept; they sought to quantify "life stress" by scoring "significant life events", and a large amount of research was undertaken to examine links between stress and disease of all kinds. By the late 1970s, stress had become the medical area of greatest concern to the general population, and more basic research was called for to better address the issue. There was also renewed laboratory research into theneuroendocrine,molecular, andimmunological bases of stress, conceived as a usefulheuristic not necessarily tied to Selye's original hypotheses. TheUS military became a key center of stress research, attempting to understand and reduce combatneurosis and psychiatric casualties.[57]
Thepsychiatric diagnosispost-traumatic stress disorder (PTSD) was coined in the mid-1970s, in part through the efforts of anti-Vietnam War activists and theVietnam Veterans Against the War, andChaim F. Shatan. The condition was added to theDiagnostic and Statistical Manual of Mental Disorders asposttraumatic stress disorder in 1980.[59] PTSD was considered a severe and ongoing emotional reaction to an extreme psychological trauma, and as such often associated with soldiers, police officers, and other emergency personnel. The stressor may involve threat to life (or viewing the actual death of someone else), serious physical injury, or threat to physical or psychological integrity. In some cases, it can also be from profound psychological and emotional trauma, apart from any actual physical harm or threat. Often, however, the two are combined.
By the 1990s, "stress" had become an integral part of modern scientific understanding in all areas of physiology and human functioning, and one of the great metaphors of Western life. Focus grew on stress in certain settings, such asworkplace stress, andstress management techniques were developed. The term also became aeuphemism, a way of referring to problems and elicitingsympathy without being explicitly confessional, just "stressed out". It came to cover a huge range of phenomena from mildirritation to the kind of severe problems that might result in a real breakdown ofhealth. In popular usage, almost any event or situation between these extremes could be described as stressful.
The American Psychological Association's 2015 Stress In America Study[60] found that nationwide stress is on the rise and that the three leading sources of stress were "money", "family responsibility", and "work".
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