Stress is not all bad. A short, intense stress, like a near miss in traffic, triggers the “fight or flight” response, and in the short term the immune system actually mobilizes. The problem is stress that never switches off.
What happens in the body
When you face a stressor, the brain activates two systems:
- The sympathetic nervous system releases adrenaline (epinephrine) and noradrenaline.
- The HPA axis (hypothalamus, pituitary, adrenal glands) releases cortisol.
Cortisol normally helps regulate inflammation and then falls back. With chronic stress, levels stay elevated or the body becomes less responsive to them. The immune system ends up in an odd state: some defenses are suppressed while low-grade inflammation stays high.
What the research shows
- More colds. In classic experiments by psychologist Sheldon Cohen, volunteers exposed to cold viruses were more likely to get sick when they reported higher, longer-lasting stress.
- Slower wound healing. Studies of caregivers of people with dementia, and of students during exams, found that small wounds healed more slowly under stress.
- Weaker vaccine responses. Chronically stressed people have produced fewer antibodies after some vaccines, such as influenza.
- Inflammation. Long-term stress is linked to higher inflammatory markers, which play a role in heart disease, diabetes and depression.
- Flare-ups. Stress can worsen conditions such as eczema, psoriasis, inflammatory bowel disease and cold sores.
Indirect effects
Much of stress’s impact comes through behavior: shorter sleep, more alcohol and smoking, less exercise, and poorer eating. Each of these weakens immune function on its own.
What helps
- Sleep 7 or more hours. Sleep is when much immune regulation happens.
- Move regularly. Moderate exercise most days is associated with better immune function and mood.
- Stay connected. Social support buffers the effects of stress in many studies.
- Practice a calming technique: slow breathing, meditation, yoga or time outdoors. Mindfulness programs have shown modest benefits.
- Limit alcohol and do not smoke.
- Eat well, with plenty of plants and fiber (foods for gut health).
- Keep up with vaccines.
When to get help
If stress feels unmanageable, lasts for weeks, or comes with anxiety, depression, panic attacks or thoughts of self-harm, talk to a doctor or mental health professional. In the US, you can call or text 988 (Suicide & Crisis Lifeline) any time. The NIMH fact sheet I’m So Stressed Out! and MedlinePlus on stress and your health offer practical next steps.
