---
title: How stress affects the body
url: https://mbmi.org/stress/effects
description: What happens in the body under stress, which systems are affected, and what the research says about long-term stress and disease risk.
author: Mind and Body content team
last_updated: 2026-10-26
---
# How stress affects the body

Stress changes the heart, the immune system, digestion, sleep and mood. Here is what happens, how it is measured, and what the research does and does not show.

## Key takeaways

- In an acute stress response, hormones raise heart rate, blood pressure and blood sugar.
- Prolonged stress is associated with higher risk of cardiovascular disease and with changes in immune function.
- Association is not proof of cause. Stress interacts with genes, behavior and circumstances.

## The stress response

When the brain perceives a threat, the sympathetic nervous system and the adrenal glands release adrenaline, noradrenaline and cortisol. Heart rate and blood pressure rise, breathing quickens, and blood is directed toward muscles.[1] (source 1)

Walter Cannon at Harvard described this as the fight-or-flight response in the early 1900s. Herbert Benson later described its counterpart, the relaxation response.


> From the MBMI Archive: [The Stress Response](https://mbmi.org/archive/mind-body-basics/stress/the-stress-response) — The institute's short primer on fight-or-flight, 2006–2009.


## What long-term stress is linked to

- Heart and blood vessels. Chronic stress is associated with higher risk of heart disease and stroke, partly through blood pressure and behavior such as poor sleep and smoking.[2] (source 2)
- Overall disease risk. Psychological stress has been associated with depression, cardiovascular disease and infectious illness, though most of this evidence shows association and not proof of cause.[3] (source 3)
- Sleep and mood. Stress can make it harder to fall asleep and is a risk factor for anxiety and depression.
- Digestion. Stress can worsen symptoms of conditions such as irritable bowel syndrome.[4] (source 4)


## How to read this evidence

Most findings come from observational studies, which show links without proving that stress caused the outcome. People under stress may also sleep less, drink more or exercise less, and those habits matter too.[3] (source 3)


## Common questions

### How do I know if stress is harming me?

Persistent sleep problems, frequent illness, ongoing tension or low mood are reasons to speak with a clinician. A clinician can also check for other causes.

### Does the body recover from stress?

Yes, generally. Recovery depends on rest, sleep, movement and support, and the relaxation response is one of the tools studied for it.


## Sources

1. McEwen BS. Protective and damaging effects of stress mediators. N Engl J Med. 1998;338(3):171–179. doi:10.1056/nejm199801153380307
2. Steptoe A, Kivimäki M. Stress and cardiovascular disease. Nat Rev Cardiol. 2012;9(6):360–370. doi:10.1038/nrcardio.2012.45
3. Cohen S, Janicki-Deverts D, Miller GE. Psychological stress and disease. JAMA. 2007;298(14):1685–1687. doi:10.1001/jama.298.14.1685
4. Lacy BE, Pimentel M, Brenner DM, et al. ACG clinical guideline: management of irritable bowel syndrome. Am J Gastroenterol. 2021;116(1):17–44. doi:10.3410/f.739215445.793582237