Chronic stress: what it actually does to your body
Short bursts of stress are not the problem. The acute stress response, a fast surge of adrenaline and cortisol, is a survival system that evolved to handle a sprint or a sharp shock and then switch off. The trouble starts when it never fully switches off. Months of low-grade activation keep stress chemistry running in the background, and over time that steady drip shows up in your heart, immune defences, gut, sleep, metabolism, skin and thinking. Researchers call the cumulative cost allostatic load.1 The encouraging part is that the load is modifiable, and a handful of unglamorous habits genuinely lower it.
Key facts
- The acute stress response is healthy and self-limiting. Chronic activation is the harmful pattern, because the body rarely gets back to baseline.1
- The cumulative wear from repeated or sustained stress has a name, allostatic load, coined by Bruce McEwen and Eliot Stellar in 1993.1
- In a pooled analysis of over 600,000 people, work stress was linked to a 10 to 40 percent higher risk of coronary heart disease and stroke.2
- In a controlled exposure study, people under more psychological stress caught more colds, in a dose-response pattern, after being given a cold virus.3
- The most effective levers are not exotic: movement, sleep, slow breathing, social connection and boundaries, each with its own evidence base.91011
Acute response vs chronic activation
When you face a sudden demand, two systems fire. First the sympathetic nervous system releases adrenaline within seconds: heart rate climbs, blood pressure rises, fuel floods the bloodstream and attention narrows. Slightly slower, the hypothalamic-pituitary-adrenal (HPA) axis releases cortisol, which sustains the response and then, working normally, signals the system to stand down. This is allostasis: the body changing its settings to meet a challenge, then returning to baseline. It is meant to be brief.
Chronic stress is what happens when the off-switch stops working. The demand does not pass, so cortisol stays elevated or its daily rhythm flattens, and the system is repeatedly called on without full recovery. McEwen and Stellar described the resulting wear as allostatic load: the price the body pays for being kept in a state of readiness it was only built to hold briefly.1 The distinction matters, because it reframes the goal. You are not trying to abolish stress, which is neither possible nor desirable. You are trying to restore recovery, so the system can come back down.
What it does, system by system
The effects below are supported by evidence of varying strength. Much of the human data is observational, so it shows association rather than proof that stress alone causes disease, but the mechanisms are well mapped.
| System | What tends to happen | Evidence |
|---|---|---|
| Cardiovascular | Higher blood pressure, raised heart-disease and stroke risk | Large pooled cohorts: roughly 10 to 40 percent excess risk with work stress.2 |
| Immune | More frequent infection; blunted response to cortisol's anti-inflammatory signal | Controlled viral-challenge studies; mechanistic work on glucocorticoid resistance.34 |
| Gut | Altered motility and sensitivity, leakier barrier, symptom flares in IBS | Strong mechanistic and clinical evidence via the gut-brain axis.5 |
| Sleep | Harder to fall and stay asleep; a vicious circle with stress | Insomnia linked to raised 24-hour cortisol; the link runs both ways.6 |
| Weight and insulin | More visceral (abdominal) fat, reduced insulin sensitivity | Mechanistic and observational; work stress also tied to type 2 diabetes.27 |
| Skin | Slower barrier repair; flares of eczema and psoriasis | Experimental and clinical evidence of stress-triggered flares.8 |
| Cognition | Worse working memory and attention; effects on memory regions | Human studies link high cortisol to memory deficits.12 |
Heart and circulation. Stress raises blood pressure and heart rate in the moment, and over years a pooled analysis of more than 600,000 people in Europe, the USA and Japan found job strain and long hours associated with a 10 to 40 percent higher risk of coronary heart disease and stroke.2 The effect was modest but consistent across sexes and age groups.
Immune defences. In a now-classic study, Sheldon Cohen's team exposed 394 healthy volunteers to a common-cold virus and found that those reporting more psychological stress were more likely to fall ill, in a clear dose-response pattern.3 Later work proposed a mechanism: prolonged cortisol makes immune cells less responsive to its anti-inflammatory signal, a state called glucocorticoid resistance, which lets inflammation run less checked.4
Gut. The gut and brain are in constant two-way conversation. Stress alters gut movement, sensitivity and barrier integrity, and is a well-recognised trigger for flares in irritable bowel syndrome.5 If your stomach is the first thing to react when life gets hard, that is the gut-brain axis at work, and our piece on whether it is IBS or SIBO goes deeper.
Sleep, metabolism and skin. Insomnia is associated with raised cortisol across the 24-hour cycle, and poor sleep and stress feed each other in a loop.6 Metabolically, sustained cortisol favours fat storage around the abdomen and works against insulin, and large studies link work stress to type 2 diabetes.27 The skin is stress-sensitive too: experimental stress slows repair of the skin barrier, and eczema and psoriasis commonly flare under pressure.8
Brain and thinking. Acutely, high cortisol can sharpen focus; chronically, it tends to impair working memory and attention, and human research links higher cortisol over time to poorer memory.12 The fuzzy thinking and short fuse of a stressful spell are real. Our article on the wired-but-tired nervous system explains why you can feel exhausted yet unable to settle.
Evidence strength, plainly. The cold-virus and work-stress findings are robust. Much of the rest is observational and cannot fully separate stress from the habits that travel with it, such as poor sleep, less exercise and more alcohol. That does not make the effects unreal: it means stress acts partly through the lifestyle it disrupts, which is also why the levers below help.
The levers that genuinely lower the load
None of these is a cure, and the effects are real but moderate. What they share is that they target recovery, helping the system return to baseline rather than masking the feeling.
- Move regularly. A network meta-analysis of 44 trials found exercise produced moderate reductions in cortisol in people with psychological distress, with gentler modalities such as yoga showing the largest hormonal effect; vigorous exercise still improved mood even where it raised cortisol acutely.9 Most weeks, aim for the kind of activity you will actually keep doing.
- Protect sleep. Because stress and sleep form a loop, steadying sleep is one of the highest-leverage moves. Regular hours, morning daylight and a genuine wind-down all help.6
- Breathe slowly. Deliberate slow breathing, around six breaths a minute for a few minutes, reliably shifts the nervous system toward its calming branch and raises heart-rate variability, a marker of recovery capacity.10 Brief one-off sessions do little; short, regular practice is what works.
- Stay connected. A meta-analysis of 148 studies found stronger social relationships associated with a 50 percent greater likelihood of survival, an effect comparable to stopping smoking.11 This is observational, but the signal is large and consistent. Loneliness and health covers the mechanism.
- Set boundaries and recover. Allostatic load is fundamentally about demand outrunning recovery, so reducing chronic demand at the source, and genuinely switching off, is not soft advice but the core mechanism.
If you want to change one thing at a time rather than overhaul everything, our getting-started guide walks through that, and you can browse more across our insights.
If stress has tipped into feeling unable to cope, persistent low mood or anxiety, or thoughts of self-harm, that warrants support, not stoicism. In England you can self-refer to NHS Talking Therapies, or speak to your GP. For urgent help, call NHS 111 and select the mental health option. In an emergency, or if life is at risk, call 999. Samaritans are free on 116 123, any time of day or night.13 These states are common and treatable, and help genuinely works.
What to ask your GP
- Could ongoing stress be contributing to my blood pressure, sleep, gut symptoms or weight, and is anything worth checking?
- Should we rule out conditions that mimic or worsen stress, such as an overactive or underactive thyroid, or anaemia?
- Am I eligible to self-refer to NHS Talking Therapies, or would you refer me?
- Are there workplace or occupational-health options that could reduce the pressure at source?
References
- McEwen BS, Stellar E, 1993. Stress and the individual: mechanisms leading to disease. Archives of Internal Medicine 153(18):2093-2101. PMID 8379800.
- Kivimaki M, Kawachi I, 2015. Work stress as a risk factor for cardiovascular disease. Current Cardiology Reports 17(9):630. PMC4523692.
- Cohen S, Tyrrell DA, Smith AP, 1991. Psychological stress and susceptibility to the common cold. New England Journal of Medicine 325(9):606-612. nejm.org.
- Cohen S, Janicki-Deverts D, Doyle WJ, et al., 2012. Chronic stress, glucocorticoid receptor resistance, inflammation, and disease risk. PNAS 109(16):5995-5999. pnas.org.
- Qin HY, Cheng CW, Tang XD, Bian ZX, 2014. Impact of psychological stress on irritable bowel syndrome. World Journal of Gastroenterology 20(39):14126-14131. PMC4202343.
- Dressle RJ, Feige B, Spiegelhalder K, et al., 2022. HPA axis activity in patients with chronic insomnia: a systematic review and meta-analysis of case-control studies. Sleep Medicine Reviews 62:101588. sciencedirect.com.
- Joseph JJ, Golden SH, 2017. Cortisol dysregulation: the bidirectional link between stress, depression, and type 2 diabetes mellitus. Annals of the New York Academy of Sciences 1391(1):20-34. PMC5334212.
- Arck PC, Slominski A, Theoharides TC, et al., 2006. Neuroimmunology of stress: skin takes center stage. Journal of Investigative Dermatology 126(8):1697-1704. PMID 16845409.
- Systematic review and network meta-analysis, 2025. The optimal exercise modality and dose for cortisol reduction in psychological distress. Sports (Basel) 13(12):415. PMC12736704.
- Laborde S, Allen MS, Borges U, et al., 2022. Effects of voluntary slow breathing on heart rate and heart rate variability: a systematic review and meta-analysis. Neuroscience & Biobehavioral Reviews 138:104711. sciencedirect.com.
- Holt-Lunstad J, Smith TB, Layton JB, 2010. Social relationships and mortality risk: a meta-analytic review. PLoS Medicine 7(7):e1000316. journals.plos.org.
- Lupien SJ, Maheu F, Tu M, et al., 2007. The effects of stress and stress hormones on human cognition. Brain and Cognition 65(3):209-237. PMID 17466428.
- NHS, 2024. Get help with stress. nhs.uk.
This article is educational and does not constitute medical advice, diagnosis, or a treatment recommendation. Medication uses described as “off-label” are not licensed for that purpose in the UK and should only be considered under qualified clinical supervision. Always speak to your GP, pharmacist, or a registered specialist before starting, stopping, or changing any treatment. If you have severe or alarm symptoms - unintentional weight loss, blood in your stool, difficulty swallowing, persistent vomiting, a fever, or severe pain - seek urgent medical care.