Psychological Stress

Abstract

Psychological stress, which MeSH classifies under psychophysiology, is the state that arises when the demands of a situation are appraised as taxing or exceeding a person's resources to cope. The construct spans three traditions. Selye described a bodily General Adaptation Syndrome to any noxious demand; Lazarus recast stress as a transaction in which cognitive appraisal, not the stimulus alone, determines the response; and McEwen traced how the mediators that protect in the short term damage the body when activated too often, the burden he named allostatic load. This article treats psychological stress as a worked case: what it means to be stressed, its measured types, the appraisal and physiological models, how stress is quantified, and why chronic stress predicts disease.

Keywords: psychological stress, allostatic load, coping

Few terms in psychology are used as loosely, or carry as much explanatory weight, as stress. In ordinary speech it names a feeling; in the clinic and the laboratory it names a process that links a person's circumstances to the activity of the brain, the endocrine system, and eventually the risk of disease. The modern construct begins with Hans Selye, who borrowed the word from engineering to describe a stereotyped bodily reaction to any sufficiently noxious demand (Selye, 1936). It was sharpened decades later by Richard Lazarus, who argued that the same external event stresses one person and not another because what matters is not the event but its appraisal — the individual's judgement of what is at stake and whether it can be handled (Lazarus & Folkman, 1984). Psychological stress, on the contemporary view, is the product of that transaction between demand and resource, and its measurement and physiology are the subject of this article (Cohen et al., 2007).

What Psychological Stress Is

Psychological stress is best defined not by the stimulus and not by the response, but by the relationship between them. Lazarus and Folkman framed it as a transaction: stress occurs when a person appraises the demands of a situation as exceeding the resources available to meet them, and so as endangering well-being (Lazarus & Folkman, 1984). This definition does two kinds of work at once. It explains why a deadline that crushes one worker energizes another, and it locates the decisive variable inside the person — in the act of appraisal — rather than in the external event, which the older stimulus-based accounts could not do.

Appraisal is held to proceed in two steps. Primary appraisal asks what is at stake: is this situation irrelevant, benign, or a threat, a harm already done, or a challenge that might be mastered? Secondary appraisal asks what can be done about it: what coping options exist, and are they adequate? Stress is the output when primary appraisal flags a threat that secondary appraisal cannot comfortably discharge. Because both steps are judgements, the same objective pressure yields different stress in different people, and in the same person at different times — which is exactly what any theory of stress must explain. The demonstration below lets the two appraisals be set independently and shows the resulting state.

Types of Psychological Stress

Beneath the descriptor, MeSH carries eight narrower kinds of psychological stress, filed on the psychophysiology and behavioral-symptom trees. They are not mutually exclusive — occupational stress may produce emotional exhaustion, and financial stress often co-occurs with caregiver burden — and the arrangement is an indexing classification of how the literature is catalogued, not a claim that these are disjoint natural kinds. Only subtypes with a live route on this site are linked; the remainder are glossed from the MeSH scope in brief.

Note. Psychological Stress is filed under both behavioral symptoms (F01.145.126.990) and psychophysiology (F02.830.900); the arrangement is a MeSH indexing classification rather than a set of mutually exclusive kinds. Only subtypes with a live route on this site are linked.

From Selye to Appraisal: Models of Stress

The scientific study of stress opens with Hans Selye, who noticed that rats exposed to very different harmful agents — cold, toxins, surgical injury — developed the same triad of adrenal enlargement, thymus shrinkage, and gastric ulceration. He concluded that the body mounts a single, nonspecific response to any sufficiently taxing demand, and named it the General Adaptation Syndrome, unfolding in three stages: an initial alarm, a resistance phase of mobilized defence, and, if the demand persists, exhaustion (Selye, 1936). Figure 1 traces these three stages against the body's baseline capacity to resist. Selye's great contribution was to make stress a measurable physiological object; his great limitation was that the response is not, in fact, wholly nonspecific, and his account left no room for the psychological fact that a demand must be perceived as threatening before it stresses at all.

Figure 1

The Three Stages of Selye’s General Adaptation Syndrome

That gap was filled by Lazarus and Folkman, whose transactional model relocated the engine of stress from the stimulus to its appraisal (Lazarus & Folkman, 1984). Where Selye's organism reacted to demands, Lazarus's person evaluated them, which is why two people in identical circumstances can differ so completely. The transactional model also gave coping a central and analyzable role: once stress is defined by appraised demand exceeding resource, the strategies a person deploys — altering the situation, reframing its meaning, or regulating the emotion it provokes — become the second half of the theory rather than an afterthought.

A third, complementary tradition is structural rather than individual. Karasek's demand-control model of the workplace predicts that strain is greatest not simply where job demands are high, but where high demands combine with low decision latitude — little control over how the work is done (Karasek, 1979). This reframes a large class of real-world stress as a property of the situation's architecture, and it anticipates the appraisal logic: control is precisely what secondary appraisal evaluates.

The Physiology of Stress and Allostatic Load

The body answers an acute stressor along two coordinated axes: the fast sympathetic-adrenal-medullary response that releases adrenaline within seconds, and the slower hypothalamic-pituitary-adrenal axis that releases cortisol over minutes. These mediators are protective. They mobilize energy, sharpen attention, and prepare the organism to act, then subside when the threat passes. The central insight of modern stress physiology, due largely to Bruce McEwen, is that the very same mediators become damaging when the response is called upon too often, goes on too long, or fails to shut off (McEwen, 1998).

McEwen and Stellar named the running cost of this chronic activation allostatic load: the cumulative wear on organs and regulatory systems that accrues when the mechanisms of short-term adaptation are chronically engaged (McEwen & Stellar, 1993). The framing inverts the older view. Stability is not maintained by holding internal conditions constant (homeostasis) but by varying them to meet demand (allostasis); the problem is not the fluctuation itself but its accumulation when recovery is denied. Allostatic load is what connects a psychological state to measurable pathology — elevated blood pressure, visceral fat, glucose dysregulation, and a remodelled stress-response system (McEwen, 1998). The demonstration below contrasts a single, recovered stress response with the accumulation that follows when stressors repeat before recovery is complete.

The mediators also reshape the brain that governs them. Chronic stress and sustained glucocorticoid exposure remodel the very regions that regulate the stress response — dendrites retract in the hippocampus and prefrontal cortex, while the amygdala, which drives threat reactivity, can grow (McEwen, 1998). The system that should switch itself off is thus progressively biased toward staying on, a feed-forward loop that helps explain why chronic stress is so corrosive and why its cognitive toll — on memory and on regulation — tracks its physiological one (O'Connor et al., 2021).

Measuring Psychological Stress

Because stress is a process rather than a thing, it is measured along several distinct axes, and a recurring methodological lesson is that these axes do not interchange (Epel et al., 2018). The oldest approach counts stressors. Holmes and Rahe's Social Readjustment Rating Scale assigns each major life event a weight in life-change units — bereavement, divorce, job loss, even positive upheavals like marriage — on the premise that any change requiring readjustment taxes the organism, and that accumulated units predict subsequent illness (Holmes & Rahe, 1967). Its strength is objectivity; its weakness is that it ignores appraisal, treating an event as equally stressful for everyone.

The second axis measures perceived stress directly. Cohen's Perceived Stress Scale asks how unpredictable, uncontrollable, and overloaded a respondent has found life in the past month — the very qualities Lazarus's appraisal theory identifies as stress-inducing — and so captures the subjective transaction the life-event checklist omits (Cohen et al., 1983). The worked example below traces its scoring, including the reverse-scored items that guard against response bias. The demonstration that follows lets each item be set and shows the total assemble.

The third axis is physiological: cortisol in saliva or hair, blood pressure reactivity, inflammatory markers, and composite allostatic-load indices that sum dysregulation across systems. These have the appeal of objectivity but are noisy and state-dependent, and they correlate only modestly with self-report — a divergence that is itself informative, since the perceived and the physiological are partly separable components of the same process (Epel et al., 2018; Crosswell & Lockwood, 2020). Best practice now treats stress as multidimensional and matches the measure to the question rather than seeking one number to stand for all of it (Crosswell & Lockwood, 2020).

Stress, Disease, and Individual Difference

The reason stress commands so much research attention is that it predicts disease. Cohen and colleagues, reviewing decades of evidence, conclude that psychological stress is a graded and plausible contributor to the onset and course of conditions as varied as depression, cardiovascular disease, and infectious illness, acting through both the physiological pathways above and the behaviours stress promotes — poor sleep, poor diet, smoking, and inactivity (Cohen et al., 2007; Cohen et al., 2019). The effect reaches to the cellular level: Epel and colleagues found that women under the highest chronic stress had markedly shorter telomeres — the protective caps on chromosomes whose shortening is a marker of cellular ageing — equivalent to roughly a decade of additional ageing (Epel et al., 2004).

Yet the relationship is not deterministic, and the same appraisal logic that defines stress also governs who it harms. The clearest demonstration is gene-by-environment interaction: Caspi and colleagues showed that stressful life events predicted depression far more strongly in carriers of a short allele of the serotonin-transporter gene than in those with the long allele, so that the same events produced different outcomes depending on an inherited moderator (Caspi et al., 2003). Whatever the status of any single genetic finding, the principle stands: stress acts on a variable organism, and the pathway from adversity to disease is shaped by appraisal, coping, genetics, and social context together (O'Connor et al., 2021).

Worked Example

Consider how the Perceived Stress Scale turns a month's experience into a single number, and why four of its items are scored backwards. The ten-item version asks, for each item, how often a feeling occurred in the past month, on a scale from 0 (never) to 4 (very often). Six items are worded negatively and scored directly — being upset by something unexpected, feeling unable to control important things, feeling nervous and stressed, feeling unable to cope, being angered by things outside one's control, and feeling difficulties piling too high. Four items are worded positively — feeling confident about handling problems, feeling that things are going one's way, feeling in control of irritations, and feeling on top of things — and these are reverse-scored, so that a high frequency of a good feeling subtracts from the stress total rather than adding to it.

Take a respondent who answers the six negative items 3, 3, 4, 3, 3, and 4, and the four positive items 1, 1, 2, and 1. The negative items are summed as they stand: 3 plus 3 plus 4 plus 3 plus 3 plus 4 gives 20. The four positive items must first be reversed by subtracting each from 4, turning the raw 1, 1, 2, 1 into 3, 3, 2, 3, which sum to 11. The full score is the two subtotals added together: 20 plus 11 equals 31, out of a possible maximum of 40.

The single fact this makes vivid is what the reverse scoring buys. A respondent who simply circled the same high number down the whole column — agreeing strongly with every item — would score high on the negative items but, because the positive items are flipped, would have those agreements subtracted back out, pulling the total toward the middle. The reversal therefore penalizes undifferentiated responding and rewards a respondent who genuinely distinguishes the stressful items from the reassuring ones, so the 31 above reflects a real pattern of high perceived stress rather than an artefact of how the form was filled in (Cohen et al., 1983). The demonstration above sets each item and shows the reverse-scored contribution separately.

Discussion

Three generations of stress research converge on a single shape. Selye established that the body responds to demand with a coordinated physiological mobilization; Lazarus established that whether a demand counts as a stressor depends on how it is appraised; and McEwen established that the protective response becomes the source of harm when it is sustained. What began as a nonspecific bodily reaction has become a process with a clear architecture: a demand, an appraisal of it against one's resources, a physiological and behavioural response, and — over time — a cumulative cost when that response cannot stand down.

This architecture explains why the field insists on measuring stress in more than one way. A life-event checklist, a perceived-stress questionnaire, and a cortisol assay are not three attempts at the same quantity; they are readings of different stages of one process, and their imperfect agreement is the point rather than a failure. It also explains why stress is a risk factor rather than a cause: it raises the probability of disease by loading a system whose vulnerability is set by genetics, history, and circumstance, so that the same adversity that sickens one person leaves another, better-resourced or differently disposed, unharmed. The practical upshot is that stress is addressable at every link in the chain — by changing the demand, supporting the appraisal, strengthening coping, or protecting recovery — which is why interventions as different as job redesign and mindfulness training can each claim a rationale.

Current Directions

The most active methodological front is the reform of stress measurement itself. A broad effort in population science argues that the field has too often treated self-reported and physiological stress as interchangeable, and calls for a unified framework that specifies which dimension of stress — exposure, appraisal, or biological response — a given study actually measures, and over what timescale (Epel et al., 2018). The practical counterpart is a growing consensus on best practice for health research: matching the instrument to the construct, combining subjective and objective measures rather than substituting one for the other, and capturing stress as it unfolds in daily life rather than only in retrospect (Crosswell & Lockwood, 2020). A second direction revisits long-held assumptions with larger and better-controlled samples; Cohen and colleagues catalogue a set of findings about stressful life events and disease risk that overturn textbook intuitions, such as the ways in which the timing and interpretation of events matter as much as their number (Cohen et al., 2019). Together these lines are turning stress from a single evocative word into a set of precisely defined and separately measurable quantities (O'Connor et al., 2021).

Common Misconceptions

All stress is harmful.

The acute stress response is adaptive, mobilizing energy and attention to meet a demand, and subsides on recovery. What damages health is chronic or repeated activation without recovery — the accumulation McEwen named allostatic load — not the single episode (McEwen, 1998).

Stress is a property of the event, so the same events stress everyone equally.

On the transactional model, stress depends on appraisal: the same objective demand stresses a person who judges it to exceed their resources and not one who judges it manageable, which is why individual difference is built into the definition rather than added to it (Lazarus & Folkman, 1984).

A high cortisol level is a direct readout of how stressed someone is.

Physiological measures and self-reported stress correlate only modestly, because they index partly separable components of the process; cortisol is also strongly state- and time-dependent, so no single assay stands in for stress as a whole (Epel et al., 2018).

Glossary

Allostasis.

The maintenance of stability through change — varying internal parameters to meet anticipated demand — as opposed to holding them constant.

Allostatic load.

The cumulative physiological wear that accrues when the mediators of the stress response are activated too often or fail to shut off after the demand has passed.

Appraisal.

The cognitive evaluation of a situation's significance for well-being (primary) and of the resources available to cope with it (secondary); the determinant of stress on the transactional model.

Coping.

The cognitive and behavioural efforts a person makes to manage demands appraised as taxing, whether by altering the situation, reframing it, or regulating the emotion it provokes.

Cortisol.

The principal glucocorticoid released by the hypothalamic-pituitary-adrenal axis during stress; protective acutely, damaging when chronically elevated.

Demand-control model.

Karasek's account of occupational strain, in which the worst outcomes arise from the combination of high job demands with low decision latitude.

Emotional exhaustion.

The depletion of emotional resources under sustained demand; the core and earliest component of burnout.

General Adaptation Syndrome.

Selye's three-stage bodily response to any sustained noxious demand, proceeding through alarm, resistance, and exhaustion.

Glucocorticoids.

The class of steroid hormones, chiefly cortisol in humans, that the adrenal cortex releases under stress to mobilize energy and modulate immune and brain function.

Homeostasis.

The maintenance of internal conditions within a narrow constant range; the classical model of regulation that allostasis extends.

HPA axis.

The hypothalamic-pituitary-adrenal axis, the slow neuroendocrine limb of the stress response that culminates in cortisol release.

Occupational stress.

Stress arising from the demands and conditions of work, shaped by the balance between those demands and the worker's control over them.

Perceived Stress Scale.

Cohen's widely used self-report instrument measuring how unpredictable, uncontrollable, and overloaded a respondent has found life in the past month.

Social Readjustment Rating Scale.

Holmes and Rahe's checklist assigning life-change units to major life events, on the premise that accumulated change predicts illness.

Stressor.

An external or internal demand that can elicit a stress response; whether it does so depends on how it is appraised.

Telomere.

The protective cap on the end of a chromosome whose progressive shortening marks cellular ageing and is accelerated by chronic stress.

Transactional model.

Lazarus and Folkman's account of stress as a relationship between a person and the environment, in which appraised demand exceeds appraised resources.

Key Researchers

Sheldon Cohen (b. 1947). Health psychologist at Carnegie Mellon University who developed the Perceived Stress Scale and showed, through controlled viral-exposure studies, that psychological stress raises susceptibility to infectious and chronic disease. Google Scholar - Faculty Page - Wikipedia - Wikidata

Elissa S. Epel (contemporary). Health psychologist at the University of California, San Francisco whose work links chronic stress to telomere shortening and who has led the reform of stress measurement in population science. Google Scholar - Faculty Page - Wikipedia - Wikidata

Richard S. Lazarus (1922-2002). American psychologist at the University of California, Berkeley who, with Susan Folkman, developed the transactional model of stress and coping, relocating stress from the stimulus to its cognitive appraisal. Wikipedia

Bruce S. McEwen (1938-2020). American neuroendocrinologist at The Rockefeller University who introduced the concept of allostatic load and mapped how stress mediators remodel the brain and body. Wikipedia - Wikidata

Robert M. Sapolsky (contemporary). Neuroendocrinologist and primatologist at Stanford University whose studies of wild baboons established how social rank and chronic stress shape glucocorticoid physiology and health. Faculty Page - Wikipedia

Hans Selye (1907-1982). Austrian-Canadian endocrinologist at the Université de Montréal who introduced the biological concept of stress and described the General Adaptation Syndrome. Wikipedia - Wikidata

Frequently Asked Questions

What is psychological stress?
Psychological stress is the state that arises when a person appraises the demands of a situation as taxing or exceeding the resources available to cope with them. It is defined by the relationship between demand and resource rather than by the external event alone (Lazarus & Folkman, 1984).

Is all stress harmful?
No. The acute stress response is adaptive and subsides on recovery. Harm comes from chronic or repeated activation without recovery, the cumulative burden that McEwen called allostatic load, rather than from any single episode (McEwen, 1998).

What is the General Adaptation Syndrome?
It is Hans Selye's description of the body's response to any sustained noxious demand, unfolding in three stages: an initial alarm, a phase of mobilized resistance, and, if the demand persists, exhaustion (Selye, 1936).

What is allostatic load?
Allostatic load is the cumulative physiological wear that builds up when the mediators of the stress response are activated too often or fail to switch off. It is the mechanism that links a psychological state to measurable disease (McEwen & Stellar, 1993).

How is psychological stress measured?
Stress is measured along several axes: checklists of major life events, self-report scales of perceived stress such as the Perceived Stress Scale, and physiological markers like cortisol. These index different parts of the process and agree only modestly (Cohen et al., 1983).

Does stress cause disease?
Stress is a graded risk factor rather than a direct cause. It raises the probability of conditions including cardiovascular disease, depression, and infection, acting through both physiological pathways and the behaviours it promotes (Cohen et al., 2007).

Can stress affect ageing at the cellular level?
Research suggests it can. Women under the highest chronic stress were found to have markedly shorter telomeres, the protective caps on chromosomes whose shortening marks cellular ageing, than less-stressed peers (Epel et al., 2004).

Why does the same event stress one person and not another?
Because stress depends on appraisal and on a variable organism. Genetic moderators, coping resources, and social context all shape the path from adversity to outcome, so identical events can produce different results (Caspi et al., 2003).

References