Cortisol, as the body’s stress hormone, often gets a bad rap. Many people assume that cortisol levels should always be non-existent, but this hormone is crucial for many things, including regulating your metabolism and blood pressure and helping you feel awake.
The highs and lows of cortisol production follow your circadian rhythm in order to regulate your sleep-wake cycle. However, if your production of cortisol is out of sync, rises too high, or remains high at night when the opposite of wakefulness is desired, the consequences can have both a direct and indirect impact on your sleep.
Cortisol and Circadian Rhythm
In order to understand cortisol’s role in sleep regulation, it is first important to understand how cortisol is connected to your circadian rhythm.
Your circadian rhythm is the 24-hour internal clock that regulates your sleep-wake cycle. One of the elements in tune with this cycle is the hypothalamic-pituitary-adrenal (HPA) axis, which is found in the brain and plays a role in regulating both sleep and cortisol production. Cortisol release is also regulated by the suprachiasmatic nucleus (SCN), a group of cells also referred to as the central pacemaker.
Both of these parts of the brain help to keep your body on its 24-hour cycle, which then dictates when cortisol is produced. Cortisol secretion is typically lowest around midnight but starts to increase about 2-3 hours after you fall asleep, continuing to rise into the waking hours with a peak around 9 a.m.
These highs and lows correlate with the function of cortisol and when the body requires it. Cortisol is highest in the morning because its primary role is to increase your alertness, making it crucial for helping you wake up in the morning. Cortisol also increases your heart and breathing rate, controls your metabolism, improves your focus, and keeps your immune system functioning properly, all actions that are needed most when you’re awake. When these actions are no longer required at a high level, such as when you’re asleep, cortisol levels lower.
Seeing this role of cortisol, it’s clear that it has a time and a place, which is why it is a part of your circadian rhythm—it rises and falls at the same time each day to increase or decrease alertness. Cortisol is necessary, but if it’s high at a time when it should be the opposite, problems can occur.
How Does Cortisol Affect Your Sleep?
Your sleep and stress response share the HPA axis, which offers an explanation for how stress can impact your sleep.
Researchers have found that an overactive HPA axis—which can result from too much stress—can disrupt sleep, causing insomnia, fragmented sleep, and less overall time spent asleep. Unfortunately, these disturbances can create even more problems for your HPA, influencing how much cortisol your body produces. Namely, studies have found that insomnia and other types of sleep deprivation can cause your body to produce more cortisol during the day, but this then poses a problem in there remaining too much cortisol in the body come bedtime, perpetuating the sleep disturbances.
High cortisol levels may also indirectly affect your sleep. For example, high cortisol can cause weight gain, and obesity is a risk factor for various medical conditions, some of which may cause poor sleep. Additionally, chronically high cortisol levels can increase inflammation, which can cause pain and discomfort, making it hard to fall asleep.
The Effect of Sleep Disorders on Cortisol Levels
While insomnia is a sleep disorder that may occur as a result of high cortisol levels, certain sleep disorders have also been shown to cause spikes in cortisol production. For example, researchers found that those with obstructive sleep apnea whose continuous positive airway pressure (CPAP) machines were withdrawn during the night had higher cortisol levels.
Evidence such as this suggests that untreated sleep disorders, which lower sleep quality, may cause cortisol levels to rise. In this way, raised cortisol levels may be a by-product of poor sleep, which can then exacerbate the problem.
How to Reduce Cortisol Levels at Night
Inflated cortisol levels are associated with poorer sleep quality, more nighttime wakings, and a harder time falling asleep, which makes methods of lowering cortisol crucial in order to sleep better at night.
Some ways to reduce your cortisol levels include:
- Lower your stress. Cortisol is the body’s stress hormone, and it can stick around longer than it should if your stress levels remain consistently high. To combat this, work on reducing your stress levels, whether that’s by spending time in nature, talking with friends and family (and laughing!), doing breathing exercises, or exercising.
- Write down your worries before bed. If you go to bed only to lie awake thinking about a million things, try to do a brain dump before hopping into bed. This allows you to get everything out on paper and ensures you don’t forget anything in the morning, creating one less worry for you.
- Create a relaxing bedtime routine. If your cortisol levels are high at night, it can be worthwhile to take the time to add some relaxation to your bedtime routine. Some possible activities to add include reading, meditating, listening to relaxing music, and doing yoga.
- Focus on your nutrition. What you eat may help lower your cortisol levels. For instance, one study found that pre- and probiotics can reduce cortisol levels. Dark chocolate and green tea, as well, may help reduce cortisol. Research has also shown that refined sugars, animal proteins, salt, and fat can increase cortisol production, so avoiding or limiting these foods may help lower your cortisol levels.
- Improve your sleep hygiene. By focusing on getting enough sleep each night, you can keep your sleep debt low, which will then keep your cortisol levels from rising too high. One way in which you can improve your sleep quality and duration is by focusing on good sleep hygiene, such as keeping your bedroom cool, dark, and quiet, following a consistent sleep schedule, and avoiding electronics at least an hour before bed.
Don’t Stress About Your Sleep
Cortisol is a vital hormone that rises and falls in accordance with our circadian rhythm—it isn’t all bad, but problems can arise if it’s high at a time when it shouldn’t be: at night.
High cortisol levels at night can create an environment that isn’t conducive to sleeping while also increasing the odds of waking during the night, all because cortisol itself is a wakefulness hormone. However, there are ways to reduce your cortisol levels, including lowering your stress levels, watching what you eat, and creating a relaxing bedtime routine.
When you focus on keeping your cortisol low before bed, you’ll be able to sleep easier and let cortisol shine at the same time as the sun.
