Your stress response is a fast survival system driven mainly by two hormones: adrenaline for the immediate surge, and cortisol for the slower, sustained phase. In short bursts it sharpens focus and readies your body to act. The harm comes when cortisol stays raised for weeks or months, because the system was never built to run continuously.
What cortisol is and what it does
Cortisol is a steroid hormone made by the adrenal glands, which sit just above the kidneys. Its release is controlled by a feedback loop between the brain and those glands, often called the HPA axis. Cortisol follows a daily rhythm: it is usually highest in the morning to help you wake, lowest overnight, and it rises further whenever the brain registers a demand.
During a challenge, cortisol keeps blood sugar available for the brain and muscles, supports alertness, and temporarily quietens functions that are not urgent, such as parts of digestion and the immune response. This is useful in a genuine emergency. The design assumes that once the pressure passes, cortisol falls back to baseline and normal function resumes. Problems tend to follow when that reset does not happen.
What happens in acute stress
When your brain perceives a threat, it acts within seconds. The first wave is adrenaline, which raises heart rate, quickens breathing, sends blood to the muscles and heightens alertness. This is the familiar surge you feel before a difficult conversation or a near miss in traffic. It is fast and it fades fast.
A slower second system follows, releasing cortisol. Cortisol keeps energy available, dampens functions that are not urgent, and helps the body sustain a response. In an acute situation this is exactly what you want, and once the threat passes, levels are meant to return to baseline. The NHS describes this everyday experience of pressure and its physical signs in its guidance on stress.
Why chronic stress is different
The problem is not stress itself; it is stress that does not switch off. When pressures are relentless, whether money, caring, work or ill health, the response stays partly activated. Cortisol that is useful in a crisis becomes a burden when it is persistently raised, and the body loses the recovery periods it depends on.
Chronic activation is associated with raised blood pressure, disturbed sleep, changes in appetite, weakened concentration and low mood. It also interacts with inflammation in the body, a link we explore in inflammation explained. The effects are real, even though stress is often dismissed as something to simply push through.
Sleep is where the loop is most obvious. Persistently raised cortisol makes it harder to fall and stay asleep, while poor sleep raises next-day stress hormones, which then makes rest harder again. Breaking that cycle is one of the most useful things you can do, and the practical steps are covered in our guides to sleep hygiene and to caffeine and sleep.
Appetite is another area where the effect shows up. Cortisol can nudge cravings towards energy-dense food and shift where the body stores fat, which is one reason prolonged stress and weight change so often go together. How strongly any of this affects a given person varies, so the honest position is that chronic stress raises risk rather than guaranteeing any single outcome. What matters is the pattern over time, not one hard week.
When stress tips into something more
Everyday stress and a diagnosable condition sit on a spectrum. Stress becomes a health issue when it stops being a response to a specific pressure and becomes a constant state: trouble sleeping most nights, difficulty switching off, physical symptoms like headaches or a racing heart, or a sense of not coping. Persistent anxiety and low mood are treatable, and reaching a clinician earlier tends to make treatment simpler.
How to lower cortisol from chronic stress
There is no single switch that lowers cortisol on demand, and supplements marketed for that purpose have little reliable support. What works is giving the stress response genuine recovery time so that levels can fall between demands. The approaches with the strongest evidence are unglamorous but effective, most cost nothing, and they tend to reinforce one another when you keep them up.
- Physical activity, which reliably lowers felt stress and improves mood, and doubles as a buffer against the physical effects. The NHS physical activity guidelines suggest at least 150 minutes of moderate activity a week for adults.
- Protecting sleep, because stress and poor sleep feed each other, and improving one usually helps the other.
- Social connection, which is one of the most consistent protective factors in the research.
- Structured psychological therapies such as cognitive behavioural therapy, which have strong evidence for anxiety and low mood and can be accessed through NHS talking therapies, often by self-referral.
- Slow breathing and mindfulness practices, which have moderate evidence for reducing the felt intensity of stress.
A realistic framing
You cannot remove all stress, and you would not want to; some pressure is normal and even useful. The goal is not a stress-free life but a stress response that switches on when needed and off when the pressure passes. Building in recovery, through movement, sleep, connection and, when needed, professional support, is what lets the system reset. Regular physical activity, covered in UK exercise guidelines explained, is one of the most reliable levers you have. If pressure has become constant rather than occasional, that is a signal to seek support, not to push harder.
