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Health, Sleep & Rest

What Is Circadian Rhythm And How It Affects Your Energy

Written by David Oscar
Mental Health Researcher
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Do you sometimes feel like you are not in sync with your brain or body? Our habits and daily activities greatly affect how we have a productive day and restful night and a balanced life generally. Some certain processes and functions happen in our bodies at different times of the day that need to be in line with our activities during those times so that we are in harmony with our internal processes and in balance with our existence.

A good example of this is the process of the body preparing for the absorption of food and the activity of eating. Circadian rhythm plays a huge role in these processes. Making sure they are synchronized with our daily activities goes a long way to helping us live a healthy, happy, and fulfilled life.

However, you may ask, “what is circadian rhythm and what exact effects does it have in our lives?”

Well, we will take an in-depth look at that to help you understand all there is to it. We will be looking at the general concept of the circadian rhythm, how it works, examples, what it is made of, how it goes out of balance, and how to restore it for a sharper brain.

What Is Circadian Rhythm?

Circadian rhythm is simply the pattern of natural changes that occur in living beings in different aspects including mentally and physically for about 24 hours. Some of the natural changes in humans include changes in body temperature, cell regeneration, hormonal changes, sleeping at night, and remaining awake during the day, to name a few.

These changes not only happen in human beings but also in plants, animals, and other living organisms like fungi. There are many other biological processes, such as absorption of food, which recur in all living things after every given period.


The word “Circadian” itself comes from the Latin names “Circa,” which means around, and “Diem,” which means a day, forming the meaning “changes around a day.” This relates to the changes that happen in a typical day in living things.[1]

The circadian rhythm is also linked to the earth’s rotation on its axis that determines the day and night since the rhythm is also affected by external factors such as light. The study of circadian rhythms is known as chronobiology.

Understanding the Mechanics of Circadian Rhythm

Ideally, circadian rhythm regulates the different processes and activities within our brain and bodies as well as in other life forms. Certain factors affect the circadian rhythm that comes from within, which include our lifestyles, eating habits, age, physical activities, and social activities.

Light is another major factor—though an external one—that plays a major role in the circadian rhythm. When our eyes sense varying degrees of light, this information is sent to a region of the brain called the suprachiasmatic nucleus (also called the SCN). It then directs the other parts of our brain and body to activate certain processes and changes that are per the brightness level of the light detected and time of the day, while making other processes that don’t match the time of the day inactive. It simply modulates activity in the body depending on the time of the day.

The suprachiasmatic nucleus is commonly referred to as the master clock, or the circadian pacemaker, and is made up of around twenty thousand neurons or nerve cells. It is located in the part of the brain called the hypothalamus. It is referred to as the master clock because it also controls the other small biological clocks that exist in organisms.

The small biological clocks are in all tissues or organs of all life forms and they involve the proteins interrelating with cells and getting the body to be more or less active. Research studies have shown that the genes that make up the biological clocks in human beings, plants, fungi, and some animals are the same.[2]


Compared to circadian rhythms, biological clocks do much bigger work as they are also responsible for the changes that happen in organisms like plants when different seasons come, making them not limited to the 24-hour cycle. Circadian rhythms are part of the effect that comes from biological clocks.

Examples in Different Forms of Life

Almost all life forms have circadian rhythms. Let’s take a look at some of them.

In Humans

The digestive system is an example of the circadian rhythm. During the period of feeding, the circadian rhythm prepares the body for the changes that are about to happen in the gut, small intestines, and large intestines, among other body parts. It influences the production of proteins, digestive juices, and other bodily substances that are needed for this process.[3]

In Plants

The Gonyaulax polyedra plant, which is an aquatic plant that produces light at night without perceptible heat or combustion, gives a good example of circadian rhythm in plants. The plant lightens up during night hours but the light becomes dim during the day. This happens almost every 24 hours.[4]

In Animals

In animals such as rodents, mammals, or birds, the circadian rhythm is seen to influence feeding patterns. Rodents are known to have a strong sense of smell at night and the presence of light that is detected by the biological clock in the hypothalamus helps them know the best time to go look for food. Circadian rhythm also plays a role in indicating their times to hibernate or be active and their mating seasons.[5]

In Fungi

Spore development, as well as liberation in fungi, are among the known circadian rhythms in organisms of this kind. The factors that influence the release of spores are light, humidity, temperature, and wind velocity, and during the day, the sensitive spores that are thin-walled, which might be damaged by sunlight, are normally released at night while the other spores, which have thick walls, are released at daytime.[6]

What the Circadian Rhythm Is Made Of

The circadian rhythm involves a lot of factors and the changes that occur within us target various parts. Here are some of them.

1. Period Genes and Cryptochrome Genes

To begin with, two essential genes play a key role—the period genes and cryptochrome genes. They are linked to the protein that fills the nucleus of a cell at night while also reducing it during the day.

2. Body Cells

There are cells in your brain that sense light and darkness and relay this information to other parts of the body to get ready for changes, such as sleeping or waking up, feeling fresh and alert, or tired. As a result of these cells, parts of your body respond to the changes and get you to either sleep or wake up.

3. Body Temperature

Using the circadian rhythm that is related to sleeping and waking up again, when you are about to sleep, your body temperature goes down so that you can fall asleep easily. When you are about to wake up, the temperature rises and you feel more wakeful and alert so that you can get up and tackle the day.

4. Hormones

The two hormones that are recognized in the sleep-wake cycle are cortisol and melatonin.

When you are about to sleep, high levels of the melatonin hormone are produced and this hormone is also affected by light. More melatonin is produced when it is dark, that is why you are always advised to turn off the lights as you go to bed. Cortisol is a stress hormone that is produced during the day, especially in the morning, and it helps you get up and running.

When the Circadian Rhythm Gets Out of Sync

There are times when the circadian rhythm is interfered with by various incidents. When the rhythm is off, many aspects of our lives are affected including our sleeping patterns, blood pressure, mental and physical health, digestion, and moods, among others.[7][8]

Here are some of the occasions where the circadian rhythm gets out of sync and the problems that come with each case:


1. Traveling Across Different Time Zones

Crossing multiple time zones in a short period can throw the sleep-wake cycle off balance. Taking intercontinental flights that get you into new locations that could be slightly ahead or behind the time of your local area of residence can make you have difficulties adjusting.

This brings about a disorder known as “jet lag” disorder. In such cases, you have trouble sleeping at night or remaining awake during the day among other difficulties. For most people, it takes about one week for their circadian rhythm to be aligned with the time zone of their new location. It may be faster or slower than that for other people.

2. Working in Rotational Shifts

People who work in shifts, mostly the night shifts, normally have a problem with irregular sleeping patterns that clash with the circadian rhythm.

Ideally, we are all programmed to work when there is natural light outside and sleep when darkness sets in. However, shift workers do quite the contrary which makes them struggle to fall asleep when others are working and be fully awake and fresh while others are sleeping. Working late hours of the night or the whole night disrupts the circadian rhythm and brings trouble in various ways including low productivity.

3. Random Light

Bright light from devices such as computers, smartphones, and tablets and the lighting in your house can affect your sleep-wake circadian rhythm.

Research shows that the circadian rhythm is usually very reactive 2 hours before you go to bed, which means that if you use these devices around this period, you are more likely to struggle to fall asleep.[9] You may end up sleeping late at night and wake up late as well.


4. Bad Sleeping Habits

Certain habits practiced at night may also mess with the natural sleeping rhythms. These night activities include eating or drinking heavily, having different sleeping times, taking stimulants, having uncomfortable sleeping conditions and environment, and doing mentally demanding tasks.

5. Medication

Certain prescription medications can affect sleeping patterns. These medications include diuretics, clonidine, beta-blockers, sedating antihistamines, Theophylline, and selective serotonin reuptake inhibitors (SSRIs).[10] Taking these may make you take longer to sleep or keep waking up at night or even wake up late in the morning.

6. Certain Health conditions

Health conditions like blindness, brain damage, dementia, or head injuries may also interfere with your circadian rhythm.

7. Stress

When you are stressed, you are constantly worried about something, and this weighs your mind and body down. As a result, you find yourself having little to no sleep at night and wake up the following day feeling moody and exhausted.

8. Changes in Various Genes

When there are changes in our genes, our biological clocks are also touched, and this can tap the rhythm out of its natural flow.

9. Aging

As we grow old, our circadian rhythms also change. This may also give us a hectic time trying to keep up with our daily activities.

Circadian Rhythm Sleep Disorders

When it comes to sleeping, certain disorders affect the sleep-wake circadian rhythm. Here they are along with their causes and symptoms.

1. Irregular Sleep-Wake Rhythm Disorder

This is a disorder that involves a lack of a proper sleeping routine. People with this disorder tend to sleep at different intervals in 24 hours. They may try their best to create a fixed sleeping routine, but it is not always easy for them to make it work.

This disorder is found in people who are old as well as those with mental health conditions, such as Alzheimer’s and brain injury. It is caused by reduced activity of suprachiasmatic nucleus neurons, limited exposure to bright light, circadian clock’s reduced response to light and other factors that influence it, and limited physical and social activity during the daytime.[11][12]

2. Delayed Sleep Disorder

This condition relates to those people who sleep later than the normal sleep time. You will find them preferring to sleep from 1 am onward, but this also affects their waking time.

While this is not a common case among adults, it affects most teenagers. The causes of this disorder are not fully established, but it is believed that it could be linked to someone’s genes, behaviors, or hidden health issues.


3. Non-24-Hour Sleep-Wake Disorder

This disorder mostly affects completely blind people, and it is where a person’s circadian rhythm is not able to work in harmony with the 24-hour cycle. People with this condition find their sleeping time being delayed by hours or minutes every time to the point where it goes all round the clock. If they try to follow a fixed sleeping time, they are deprived of sleep constantly.

4. Advanced Sleep Phase Disorder

This is a disorder where a person starts feeling sleepy in the afternoon or early evening. People with this condition cannot be active during these times, and depriving themselves of sleep so that they sleep at the normal sleeping time does not seem to help much.

The good thing is that just as they sleep early in the evening, they also wake up early in the morning. However, if they happen to wake up too early, they can’t go back to sleep again.

The circadian rhythm in such people is advanced, making them do things earlier than normal. This problem exists in few middle-aged people and older adults.

Restoring the Circadian Rhythm for a Sharper Brain

Good sleep, proper flow of activities through the day, and other healthy practices account for a sharper brain. If your circadian rhythm is off, there are certain practices that you can do to help promote a smoother natural flow that in turn strengthen your brain.

While these practices don’t help with all cases of unhealthy circadian rhythm, they go along way in solving many possible situations that are negatively impacting it. You are strongly encouraged to make use of them to help you improve your brain and body as a whole.


Here are the practices:

  • Try to follow a fixed daily schedule. Set your alarm to wake up at the same time every day. Go to bed about the same time each day. It helps your circadian rhythm to take clues on your sleep-wake cycle.
  • Spend 20 to 30 minutes every day on physical exercise.
  • Eat healthy foods while avoiding having too much during night hours.
  • Avoid taking stimulants like coffee before going to bed.
  • Reduce the length of your naps and avoid them late in the afternoon.
  • Avoid using your devices or being exposed to any bright artificial light 2 hours before sleeping.
  • Make sure your bed is comfortable and the bedroom is quiet, dark, and sleep-friendly.
  • Expose yourself to plenty of sunlight in the morning when you wake up and during the day.
  • Avoid any activities that are not related to the essence of your bedroom when you are already in bed.
  • Do a bit of reading, meditation, and stretching before sleeping.

Since we all have different brain and body chemistry, you should feel free to test out the tips above and determine which ones go well with you and stick to them.

If you have consistent troubles with your health relating to your circadian rhythm, please visit your doctor for diagnosis and professional medical treatment.


In summary, maintaining a healthy circadian rhythm will allow you to make the most of your brain and body and also help you have an easy time sleeping when you need to be asleep and remaining awake, active, and productive during the day.

A healthy lifestyle contributes to working your circadian rhythm right and makes for a fruitful day and improved overall well-being.

Featured photo credit: Kalegin Michail via unsplash.com


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