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    Stress and the body: what happens, from cortisol to chronic stress

    Stress is the body's response to a challenge or threat: hormones such as adrenaline and cortisol sharpen alertness, tense the muscles and speed the pulse.[1][2] That response helps in the short term, but WHO and MedlinePlus say stress that persists for weeks or months can harm physical and mental health.[3][4]

    Editor reviewedStrict sourcingUpdated ExplainerMental health, Health and medicine, Life sciences

    Stress is a built-in survival response. WHO defines it as worry or mental tension caused by a difficult situation, and describes it as a natural reaction that prompts people to deal with challenges.[5] This explainer covers what happens in the body during stress, why the same system that protects us can cause harm when it stays switched on, and where stress ends and an anxiety disorder begins.

    This page is general information, not medical advice. If stress is affecting your health or daily life, talk to a doctor or other clinician.

    The stress response

    When you face a threat or a deadline, your body releases stress hormones such as adrenaline and cortisol.[1] These make your brain more alert, tense your muscles and raise your pulse, which helps you deal with the situation.[2] You may notice a faster heartbeat or sweating.[1]

    Cortisol is made by the adrenal glands, two small glands above the kidneys. Besides helping the body respond to stress, it helps control inflammation, blood sugar and blood pressure.[6]

    Two linked systems carry the response. In the hypothalamic-pituitary-adrenal (HPA) axis, corticotropin-releasing factor (CRF) starts a cascade that ends with the adrenal cortex releasing glucocorticoid hormones such as cortisol.[7][6] The pituitary hormone ACTH sets how much cortisol the adrenals make.[6] Glucocorticoids then feed back to limit the size and length of their own release.[8] In parallel, brainstem noradrenergic neurons and sympathetic-adrenomedullary circuits also carry the response, and parasympathetic systems are involved too.[8]

    Acute versus chronic stress

    MedlinePlus distinguishes acute stress, which is short-term and passes quickly, from chronic stress, which lasts for weeks or months.[9] WHO says a little stress can help people perform, but too much can cause physical and mental health problems.[3]

    With chronic stress the body stays on alert even when there is no danger.[4] MedlinePlus lists warning signs such as headaches, aches and pains, tiredness, sleep problems, an upset stomach, forgetfulness and using alcohol or medicines to relax.[10] Common causes include work, family, money and health problems; even happy events such as a wedding or a new baby can be stressful.[11]

    The neuroscientist Bruce McEwen called the cumulative cost of repeated or prolonged stress “allostatic load”: stress hormones protect in the short run, but over time the load causes bodily changes that can lead to disease.[12] He argued that everyday stressors, not just dramatic events, sustain this activity and drive poor sleep, overeating and other harmful behaviours.[13] He also described the brain as the key organ of stress, since it decides what is threatening, and noted that the hippocampus, amygdala and prefrontal cortex remodel under stress.[14] These reviews describe mechanisms; they do not by themselves show that stress caused any one person’s illness.

    What chronic stress is linked to

    MedlinePlus says chronic stress raises the risk of high blood pressure, heart disease, diabetes, obesity, depression or anxiety, skin problems and menstrual problems, and can make existing conditions worse.[4] WHO adds that chronic stress can increase the use of alcohol, tobacco and other substances.[3] NIMH lists effects on sleep and on the immune, digestive, cardiovascular and reproductive systems when anxiety does not go away.[15]

    Sleep matters too. A 2020 study found that sleep loss raised next-day anxiety through reduced activity in the medial prefrontal cortex, and that even small night-to-night drops in sleep predicted higher anxiety the following day.[16]

    Work can also be a source of stress. WHO lists excessive workloads, low job control, job insecurity, discrimination and inequality as risks to mental health.[17] See also burnout explained.

    When stress becomes something more

    NIMH describes stress as a response to an external cause, and anxiety as the body’s reaction to stress that can persist without a current threat.[18] WHO says stressful situations can cause or worsen mental health conditions, most often anxiety and depression, which need health care.[19] NIMH suggests a person may be at risk of an anxiety disorder if stress feels unmanageable and its symptoms interfere with daily life, cause avoidance or never seem to lift.[20] See the anxiety crash course for how anxiety disorders are diagnosed and treated.

    Managing stress

    NIMH suggests keeping a journal, using relaxation or mindfulness exercises, exercising, eating regular meals, keeping a sleep routine, limiting caffeine, challenging unhelpful thoughts and leaning on supportive people.[21] How strong the evidence is varies by technique. Our stress-management evidence review weighs exercise, sleep, mindfulness, breathing and workplace changes.

    Next in the crash course

    Questions readers ask

    What is stress?

    WHO defines stress as a state of worry or mental tension caused by a difficult situation, and calls it a natural response that prompts people to deal with challenges and threats.[5]

    Is stress the same as anxiety?

    Not quite. NIMH describes stress as a response to an external cause, and anxiety as the body's reaction to stress that can continue even when there is no current threat. Persistent anxiety that interferes with life may be an anxiety disorder.[18][20]

    What does cortisol do?

    MedlinePlus describes cortisol as an adrenal hormone that helps the body respond to stress, reduce inflammation and control blood sugar and blood pressure. A pituitary hormone, ACTH, sets how much is made.[6]

    Is some stress good for you?

    WHO says a little stress can help people perform daily activities, but too much can cause physical and mental health problems.[3]

    What health problems are linked to chronic stress?

    MedlinePlus lists high blood pressure, heart disease, diabetes, obesity, depression or anxiety, skin problems and menstrual problems. WHO adds that chronic stress can worsen existing conditions and increase alcohol and tobacco use.[4][3]

    When should I get help for stress?

    NIMH suggests talking to a professional if you are struggling to cope, or if stress symptoms interfere with everyday life, make you avoid things or seem always present.[20]

    Sources

    · 21 claims from 6 publishers

    Each numbered claim is a statement we checked against the sources listed with it. Tap a number in the text to see its sources in place.

    1. [1]

      The NHS says that when people feel anxious or scared the body releases stress hormones such as adrenaline and cortisol, which can cause a faster heartbeat or sweating. confirmedas of 2026-10-11

      • Stress · NHS (nhs.uk) · Stress (retrieved 2026-10-11)
    2. [2]

      MedlinePlus says the body reacts to stress by releasing hormones that make the brain more alert, tense the muscles and raise the pulse, which helps in the short term. confirmedas of 2026-10-11

      • Stress and your health · MedlinePlus (US National Library of Medicine) · Stress and your body (retrieved 2026-10-11)
    3. [3]

      WHO says a little stress can help people perform daily activities but too much can cause physical and mental health problems, and that chronic stress can worsen existing health problems and increase alcohol, tobacco and other substance use. confirmedas of 2026-10-11

    4. [4]

      MedlinePlus says chronic stress keeps the body alert without danger and over time raises the risk of high blood pressure, heart disease, diabetes, obesity, depression or anxiety, skin problems and menstrual problems. confirmedas of 2026-10-11

      • Stress and your health · MedlinePlus (US National Library of Medicine) · Stress and your body (retrieved 2026-10-11)
    5. [5]

      WHO defines stress as a state of worry or mental tension caused by a difficult situation, and calls it a natural human response that prompts people to address challenges and threats. confirmedas of 2026-10-11

    6. [6]

      MedlinePlus describes cortisol as a hormone made by the adrenal glands that helps the body respond to stress, reduce inflammation, and control blood sugar and blood pressure, with the pituitary hormone ACTH setting how much is made. confirmedas of 2026-10-11

      • Cortisol Test · MedlinePlus (US National Library of Medicine) · What is a cortisol test? (retrieved 2026-10-11)
      • Cortisol Test · MedlinePlus (US National Library of Medicine) · What is a cortisol test? (retrieved 2026-10-11)
    7. [7]

      In the stress response, corticotropin-releasing factor (CRF) from the hypothalamus drives the hypothalamic-pituitary-adrenal (HPA) axis, a cascade that ends in the release of glucocorticoid hormones from the adrenal cortex. confirmedas of 2006-12-01

    8. [8]

      Glucocorticoids feed back to limit how much and how long the HPA axis releases them, and the stress response also involves brainstem noradrenergic neurons, sympathetic-adrenomedullary circuits and the parasympathetic system. confirmedas of 2006-12-01

    9. [9]

      MedlinePlus distinguishes acute stress, which is short-term and goes away quickly, from chronic stress, which lasts weeks or months and can lead to health problems if not managed. confirmedas of 2026-10-11

      • Stress and your health · MedlinePlus (US National Library of Medicine) · Considerations (retrieved 2026-10-11)
      • Stress and your health · MedlinePlus (US National Library of Medicine) · Considerations (retrieved 2026-10-11)
    10. [10]

      MedlinePlus lists signs that stress may be affecting someone, including headaches, frequent aches, tiredness, sleep problems, upset stomach, forgetfulness and using alcohol or medicines to relax. confirmedas of 2026-10-11

      • Stress and your health · MedlinePlus (US National Library of Medicine) · Signs of too much stress (retrieved 2026-10-11)
    11. [11]

      The NHS lists work, family, financial problems and health as common causes of stress, and notes that positive life events can also be stressful. confirmedas of 2026-10-11

      • Stress · NHS (nhs.uk) · Identifying the cause (retrieved 2026-10-11)
    12. [12]

      Neuroscientist Bruce McEwen described stress hormones as protective in the short run but, through cumulative wear and tear he called "allostatic load", able to cause bodily changes that lead to disease in the long run. confirmedas of 2006-12-01

    13. [13]

      McEwen wrote that it is not only dramatic events but many daily stressors that sustain physiological activity and lead to poor sleep, overeating and other health-damaging behaviours. confirmedas of 2006-12-01

    14. [14]

      McEwen argued that the brain is the key organ of stress because it decides what is threatening and drives the physiological and behavioural responses, and that the hippocampus, amygdala and prefrontal cortex remodel in response to stress. confirmedas of 2006-12-01

    15. [15]

      NIMH says anxiety that does not go away and interferes with life could cause problems with sleep and with the immune, digestive, cardiovascular and reproductive systems, and raise the risk of an anxiety disorder or depression. confirmedas of 2026-10-11

    16. [16]

      A 2020 Nature Human Behaviour study linked sleep loss to next-day anxiety via impaired medial prefrontal cortex activity, and found that even modest night-to-night reductions in sleep predicted day-to-day increases in anxiety. confirmedas of 2020-01-01

    17. [17]

      WHO lists discrimination and inequality, excessive workloads, low job control and job insecurity as features of poor working environments that pose a risk to mental health. confirmedas of 2026-10-11

    18. [18]

      NIMH defines stress as a physical or mental response to an external cause, and anxiety as the body's reaction to stress that can occur even when there is no current threat. confirmedas of 2026-10-11

    19. [19]

      WHO says stressful situations can cause or worsen mental health conditions, most commonly anxiety and depression, which need access to health care. confirmedas of 2026-10-11

    20. [20]

      NIMH says a person may be at risk for an anxiety disorder if stress feels unmanageable and its symptoms interfere with everyday life, cause avoidance or seem always present. confirmedas of 2026-10-11

    21. [21]

      NIMH's suggestions for coping with stress include keeping a journal, relaxation or mindfulness apps, exercise, regular meals, a sleep routine, limiting caffeine, challenging unhelpful thoughts and reaching out to supportive friends or family. confirmedas of 2026-10-11

    Revision history (1)
    1. Page created.

    Created Oct 11, 2026. Last reviewed by an editor on Oct 11, 2026. Next scheduled review: Apr 11, 2027.

    Cite this page

    "Stress and the body: what happens, from cortisol to chronic stress." ContentLora, updated Oct 11, 2026. https://contentlora.com/explain/stress-and-the-body

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