Cortisol is called the stress hormone, and a lot of people want to lower it. But cortisol isn't the enemy. It helps your body wake up, mobilize energy and handle strain. It's supposed to be high in the morning and drop over the course of the day.
What seems to matter most is the rhythm. A large review of 80 studies found that a flatter curve, where cortisol doesn't drop properly toward evening, was linked to poorer health, most clearly for the immune system and inflammation. Sleep plays a part too: after a night of too little sleep, cortisol was higher the following evening.
Pick one way to support the rhythm:
- Sleep first if you sleep too little or at irregular times.
- Winding down in the evening if you're still wired when it's time to sleep.
- Movement if you sit a lot.
- Remove one long-term source if the stress never lets up.
A first step today: decide on a time when your evening starts, one hour before bedtime, and put your phone out of reach then.
Very high cortisol over a long period can be caused by illness, and it isn't something you can judge on your own. If you suspect it, have a doctor run tests.
Cortisol is often called the stress hormone, and searches for how to lower it are among the most common when it comes to stress. But the goal of lowering cortisol rests on a misunderstanding. Cortisol isn't the enemy. It helps your body wake up, mobilize energy and handle strain, and we couldn't get by without it. What seems to matter most for your health isn't how high it is, but whether it follows its rhythm. This article explains that rhythm, what research says about it and about sleep, and four ways to support it. How to handle the stress itself is covered in managing stress.
Cortisol is supposed to rise and fall
For most people, cortisol rises sharply shortly after waking, then drops over the day to a low level in the evening and at night. The morning peak helps your body get going. The low level in the evening makes room for sleep and recovery.
A stress spike in the middle of the day, before a meeting or a difficult conversation, is normal and passes. What's harder on the body is when the stress never ends and the rhythm starts to flatten: a little lower in the morning, a little higher in the evening.
The flat curve
In 2017, Adam and colleagues reviewed the results of 80 studies on the daily cortisol curve and health. A flatter curve, where cortisol didn't drop properly from morning to evening, was linked to poorer health in ten of the twelve areas examined, both mental and physical. The link was clearest for the immune system and inflammation.
The effects were small, and the studies show associations. The researchers discuss whether the flat curve is a cause or a sign that something else has fallen out of balance, probably both. But they point to something many people recognize: stress takes its toll when the body never gets to wind down.
Sleep and evening cortisol
Sleep is one of the things that most clearly affects the rhythm. In 1997, Leproult and colleagues had young men sleep normally, sleep half the night or not sleep at all, and measured their cortisol for more than a full day. After both half a night and a full night of sleep loss, cortisol was higher the following evening, and the body entered the calm phase of the night later. The study was small and involved healthy young men, but it shows why a short night can leave the next evening more wired, and the next night harder.
It easily turns into a vicious circle. Stress makes it harder to sleep, and lack of sleep makes the evening more stressful. That's why sleep is often the best place to start.
Four ways to support the rhythm
There's no single approach that works for everyone. Choose based on what seems to be flattening your curve.
Sleep first. For you if you sleep too little or at irregular times. Go to bed and get up at roughly the same time every day, weekends included. Most adults need between six and nine hours, and a good sign is that you feel alert during the day. Why bedtime so often slips is covered in putting off bedtime. First step: choose a bedtime for the week and set a reminder half an hour before.
Winding down in the evening. For you if you're still wired when it's time to sleep. Your evening needs a transition: a point when work, the news and the feed come to an end. Bright light and screens late in the evening make it harder to come down. First step: decide on a time when your evening starts, one hour before bedtime, and put your phone out of reach then.
Movement. For you if you sit a lot. Regular movement helps your body handle strain and often makes it easier to sleep. A brisk walk is enough, which is what walking as exercise is about. First step: take a brisk twenty-minute walk today, ideally in daylight.
Remove one long-term source. For you if your stress never lets up, and this is the most demanding path. No sleep routine is enough against a daily life that's overloaded month after month. Find one thing that keeps your body on alert and that can be changed: a workload to talk about, a commitment to step away from, a conflict to deal with. If the stress comes from work, read stress at work and burnout. First step: write down what has stressed you most over the past month and circle one thing you can influence.
When it might be more than stress
Be careful with supplements and quick fixes that promise to lower cortisol, and talk to a doctor before you take anything. Very high cortisol over a long period can be caused by illness, and you can't judge that yourself based on tiredness or stress. If you suspect it, or if you notice changes in your body you don't understand, have a doctor assess you and run tests.
If the stress lasts for weeks and affects your sleep, memory and daily life, talk to a doctor or health professional. If it's an emergency, call your local emergency number.
A first step today: decide on a time when your evening starts, and put your phone out of reach then.
If you're wondering how stress shows up in the rest of your body, the next part of the series covers symptoms of stress.
This is the understanding and a first step. Atlas is where it becomes a habit. Under Inner State, you use Inner weather to rate how you're doing inside and see the curve over days and weeks, and Calm breathing helps your body come down when it gets wound up. If you add Health & training, you'll find Rested? there, so you can put your sleep side by side with how you feel. Try Atlas free for 7 days, and cancel whenever you like.