What Is Stress? How It Affects Your Body and Mind
Updated · 4 min read · By Taohidul Islam
Stress is your body's response to a demand or threat. The World Health Organization describes it as a state of worry or mental tension caused by a difficult situation. Short bursts of stress are normal and can even help you perform, but stress that goes on for weeks or months can affect sleep, mood, digestion and heart health.
Stress vs. anxiety
The two are related but not the same. According to the U.S. National Institute of Mental Health, stress is usually a response to an outside cause, such as a deadline or an argument, and it tends to fade once the situation is resolved. Anxiety is a persistent worry that can continue even when there is no clear threat. Everyone feels stress from time to time. Anxiety that is constant or gets in the way of daily life may be an anxiety disorder, which a professional can assess.
What happens in your body during stress
When your brain senses a threat, it triggers the "fight-or-flight" response. Your adrenal glands release adrenaline, which:
- speeds up your heart and raises blood pressure
- makes you breathe faster
- sharpens your senses
- releases stored sugar and fat for quick energy
If the threat seems to continue, a second system (the hypothalamus, pituitary gland and adrenal glands, known as the HPA axis) keeps releasing cortisol to hold you on alert. Once the threat passes, cortisol falls and the body settles. This system works well for short emergencies. Problems arise when it switches on again and again for everyday pressures and never fully switches off.
Acute vs. chronic stress
Acute stress is short-term: a job interview, an exam, a near-miss in traffic. It passes, and it can sharpen focus.
Chronic stress lasts weeks or months: ongoing money worries, a difficult job, caring for someone who is ill, or a strained relationship. Harvard Health notes that repeated activation of the stress response is linked to high blood pressure, changes in the arteries, and brain changes associated with anxiety and depression. Higher cortisol can also increase appetite and fat storage. Chronic stress affects sleep and the immune and digestive systems too.
Common signs of stress
In your body
- Headaches, tight shoulders or jaw clenching
- Trouble falling or staying asleep
- Tiredness that rest does not fix
- Upset stomach or changes in appetite
- Getting sick more often
In your mood and thinking
- Irritability or a short temper
- Feeling overwhelmed or on edge
- Racing thoughts or constant worry
- Trouble concentrating or making decisions
In your behavior
- Pulling away from friends or activities
- Putting things off
- Drinking more alcohol, smoking or using other substances to cope
- Eating much more or much less than usual
Many of these signs have other causes, so they are a prompt to pay attention rather than proof of anything.
How to manage stress
Public health bodies, including the WHO and NIMH, point to the same practical habits.
In the moment
- Slow your breathing. A few minutes of slow, steady breaths can help you feel calmer. Our guide to breathing exercises for stress has step-by-step techniques.
- Move. A brisk walk helps release muscle tension.
- Step away briefly. Even a few minutes outside or away from a screen can reset your focus.
Day to day
- Keep a routine with regular times for meals, activity and rest.
- Protect your sleep with a consistent bedtime and wake time, and less caffeine, alcohol and screen time late in the evening.
- Exercise regularly. Walking counts.
- Eat regular, balanced meals and drink enough fluids.
- Stay connected with people you trust and talk about how you feel.
- Limit news and social media if they add to your stress.
- Write things down. A journal or to-do list can take worries out of your head and make problems feel more manageable.
When to talk to a professional
Reach out to a doctor or mental health professional if:
- stress feels unmanageable or has lasted for weeks
- it is affecting your work, relationships or ability to get through the day
- you are avoiding things you used to do
- you are relying on alcohol or drugs to cope
- you have physical symptoms that worry you, such as chest pain or a racing heart (chest pain needs urgent care)
Talking therapy, and sometimes medication, can help a great deal. Asking for help early is a sensible step, not a failure.
If you are in crisis or thinking about harming yourself, get help now. In the US, call or text 988 to reach the Suicide and Crisis Lifeline. Elsewhere, contact your local emergency services.
What a wearable can and cannot tell you
Stress often shows up in your body: resting heart rate may run higher and heart rate variability (HRV) may run lower than usual, and sleep may suffer. But the same changes can come from a hard workout, alcohol, caffeine, a poor night or an oncoming cold. A number on your wrist cannot tell you how you feel or why. It is most useful as a nudge to check in with yourself. Our HRV guide explains what that metric means.
FitRest shows a daily Stress score on the Dashboard alongside your Recovery and Sleep scores, with a 24-hour view so you can see which parts of the day ran higher for you. You can also keep a Stress widget on your iPhone or a complication on your Apple Watch. The score is a wellness guide, not a medical assessment. See how the daily scores fit together on the Recovery score page.
Sources
FitRest is a wellness app, not a medical device. It does not diagnose, treat or prevent any condition. Talk to a qualified health professional about any health concern.