What is Circadian Rhythm and its Effects on Cortisol Levels?

By Rebalance Health

October 18, 2022

Ever wondered why kids seem to naturally get sleepy as the sun goes down and wake up when the sun comes up, while their parents groan for more hours of sleep? It’s because their cortisol is in sync with their circadian rhythm. Most adults, though, are not living in rhythm because of the day-to-day stress of life and this kicks up cortisol levels. But what is the circadian rhythm and its effects on cortisol levels?  

Your circadian rhythm is part of your body’s internal clock, regulating the cycles of alertness and sleepiness within a  24-hour cycle.

Cortisol, can have a major impact on your sleep-wake cycle, leading to sleep disturbances that can negatively impact your physical and mental health. Balancing cortisol levels in your body can set your circadian clock to help minimize sleep disturbances and maximize your sleep, focus and energy. But they work hand-in-hand.

What is Circadian Rhythm?

Your body’s biological rhythms are a series of bodily functions that are regulated by an internal clock in your brain known as the suprachiasmatic nucleus (SCN), located in your hypothalamus. There are four biological rhythms which include circadian rhythms, diurnal rhythms, ultradian rhythms and infradian rhythms.

Circadian rhythms include 24-hour cycles, while diurnal rhythms are closely synced with day and night and involve a cortisol diurnal rhythm that keeps you balanced throughout a 24-hour period.

Ultradian rhythms are biological rhythms with a shorter period and higher frequency than circadian rhythms, like your heartbeat or digestion patterns. Meanwhile, infradian rhythms are biological rhythms that last more than 24 hours, such as the menstrual cycle.

As night turns into day, and day turns into night, most living beings follow a fixed circadian rhythm. This circadian cycle allows them to ensure that their body functions as they should at various points during a 24-hour period. 

Your brain will receive signals throughout your day, often based on the time of day and how the light changes throughout the day.  

For example, one important factor influencing your circadian rhythm is the natural light of day or the dark of night. In the mornings, as light peaks through your windows, your brain will tell your cells to “wake up”, enabling you to become more alert and begin your day.

In contrast, as the sun begins to set, your brain will instruct your cells to “slow down”, allowing your body to prepare for sleep. At the same time, the hormone melatonin – also known as the sleep hormone – will begin to increase, further prompting your body to sleep.

Hormones and Your Circadian Rhythm

Once you understand what the circadian rhythm is, it’s important to understand the factors that may influence your circadian clock.

While many factors can influence your sleep-wake cycle including your environment, daily routine and stress, there are also multiple hormones that play a vital role in controlling your circadian cycle.

These hormones are responsible for maintaining your body processes, including but not limited to:

  • Hunger and appetite
  • Muscle and tissue repair
  • Your sleep-wake cycle
  • Sexual functioning
  • Stress response
  • Body temperature


Melatonin, also known as the sleep hormone, is produced by the pineal gland in your brain and plays a vital role in regulating your sleep-wake cycles. Darkness will activate the production of melatonin while daylight will cause melatonin production to decline as your body gets ready to wake up.


Cortisol is supposed to work alongside melatonin to help maintain a healthy circadian cycle. But there is a cortisol’s rhythm works best when synced with your circadian rhythm, having a big impact on your sleep-wake cycles.

For example, your cortisol levels will vary throughout a 24-hour period. Upon waking, your cortisol levels should temporarily increase, helping you to feel awake and alert.

As your day comes to an end, your body’s cortisol production should slow down while your melatonin production increases, allowing your body to relax and prepare for sleep. Therefore, a healthy cortisol rhythm can support healthy sleep-wake cycles.


Human growth hormone, also known as (hGH), helps regulate body composition, body fluids, muscle and bone growth, sugar and fat metabolism, and contributes to a healthy circadian rhythm. Your growth hormone levels peak right as you’re falling asleep and remain elevated during the night. Getting adequate and quality sleep mean your body creates hGH which can promote muscle growth and repair, support a healthy metabolism, and contribute to a healthier sleep-wake cycle.

Research shows that people with frequently disturbed sleep patterns may have lower nighttime growth hormone levels compared to people with healthy sleep patterns.

Decreased growth hormone levels in adults may lead to higher levels of body fat, decreased lean muscle mass, reduced bone density, lower energy levels and diminished exercise performance.

Leptin and ghrelin

Leptin and ghrelin are two key hormones that are involved in appetite and metabolism regulation. While you sleep, your leptin levels increase to remind your brain that you are not hungry and that there is no need to eat at this time. Ghrelin, on the other hand, has the exact opposite of leptin; it tells your brain that you need to eat.

When your circadian rhythm is off and you don't get enough sleep, the result can be too little leptin in your body which can trigger hunger, overeating and a metabolism slow-down. Additionally, while sleeping, your ghrelin levels decrease, and a lack of sleep may result in too much ghrelin in your system. This can also lead to overeating and a sluggish metabolism. 

How Cortisol Affects Your Circadian Rhythm

Your circadian rhythm and the stress response both share the HPA axis – where cortisol is produced –  allowing them to influence each other. Every 24 hours, corresponding with nighttime and daytime, your body enters a period of sleep followed by a waking period and the production of cortisol in your body follows a similar pattern. 

Cortisol can help you wake up and is, therefore, highest in the morning. However, studies have shown that sleep disturbances may cause your body to increase cortisol production during the day, in an effort to keep you awake and alert. And not decrease when it’s supposed to so that you wake in the middle of the night with a racing mind.

Imbalances in your cortisol production can wreak havoc on your circadian rhythm making you too alert or too tired at the wrong time. If your cortisol levels are higher before bedtime, this can lead to a tired and wired feeling and thus no sleep. 

Circadian Rhythm

How to Balance Cortisol and Your Circadian Rhythm: 6 Key Tips

You may be wondering how to reset your circadian rhythm. Consider these steps so you can take to help balance your cortisol and in turn, create a healthy sleep-wake cycle:

Optimize your sleep hygiene

Sleep hygiene, also known as healthy sleeping habits, includes routines and environments that promote consistent and uninterrupted sleep. Ways to optimize your sleep hygiene include going to bed and waking up at the same times each day, limiting or eliminating caffeine and alcohol intake in the evening and maintaining a relaxing bedroom environment. 

Getting the right kind of 7-8 hours of sleep makes a difference. Starting your bedtime at 1am isn’t going to help your circadian rhythm, no matter how many hours of sleep you get.

Speak with your doctor

Your doctor can order tests to evaluate hormones which may be a factor in sleep disturbances. Additionally, discussing your concerns with your doctor can uncover underlying health issues like sleep apnea or an anxiety disorder. 

Unplug electronics in the evening

Screen time, whether in the form of television, cell phone, tablet, or computer, will expose you to blue light which can interfere with your circadian rhythm, and reduce your melatonin production.

Studies show that screen time before bed can increase the amount of time it takes to fall asleep, diminish sleep quality and affect concentration the following day. Try to avoid all screens and bright lights at least one hour before bedtime.

Regular exercise

You may be wondering how exercise affects circadian rhythm? Have you ever experienced a euphoric feeling after working out? If so, you can thank the release of feel-good neurotransmitters called endorphins. Endorphins are chemicals in your brain that can elevate your mood, reduce stress and improve your sleep quality. 

Reduce stress

Learning to relax by practicing things like yoga, meditation and deep breathing will go a long way in lowering your cortisol levels and helping to support a healthy circadian rhythm. 

Take the right supplements

Supplements that are designed to help restore your sleep by balancing hormones may be exactly what you need to get your circadian rhythm back on track.

An imbalanced circadian rhythm can lead to a grueling night of tossing and turning. Rebalance’s DREAM provides reishi mushroom and phosphatidylserine to help you feel calmer and achieve the deep, restorative sleep you need.

Ultimately, You need to have a system that works for you 24/7 alongside your circadian rhythm. We created the Rebalance System™ to work in sync with your circadian rhythm and bring cortisol levels back into balance.

Like most things in your body, cortisol levels can affect your circadian rhythm. Trying to reduce those cortisol levels will help balance your circadian rhythm and restore your health and wellbeing, so you can get or keep it up for good.



DREAM supports your body by lowering cortisol and rebalancing your hormones naturally, so you feel calm and confident. Formulated by doctors and scientists, our lozenges are made of natural ingredients.

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