Have you ever had jet lag or felt “off” for days after the switch to daylight saving time? That’s what happens when your circadian rhythms are out of sync. Think of circadian rhythms as your body’s biological clock—any disruption can affect sleep and overall health.

These natural rhythms rise and fall in a 24-hour cycle, drive physical and mental changes, and affect behavior. Circadian rhythms prompt us to sleep at night and wake up in the morning. They also play a role in releasing hormones, eating patterns and digestion, and body temperature.

This article discusses circadian rhythms, what disrupts them, and how to reset your internal clock.

Emmanuel Faure / Getty Images


What Are Circadian Rhythms?

Circadian rhythms are natural processes that affect humans, animals, plants, and even microbes. A master clock in your brain coordinates the rhythms. In humans and all vertebrates, the master clock is a group of about 20,000 nerve cells in the hypothalamus.

Your internal clock tries to sync the sleep and wakefulness cycle to environmental cues, such as light vs. darkness, eating patterns, and physical activity. Exposure to light in the morning moves the body toward wakefulness and helps you feel more alert and active. The setting sun tells the body to release more melatonin, a hormone that promotes sleep.

A sleep phenotype (or chronotype) is an observable pattern of behaviors linked to genetics. For example, you may have inherited the tendency to be an early bird, a night owl, a daytime napper, or a short-duration sleeper.

Circadian rhythms are crucial to the sleep-wake cycle. About every part of your body relies on circadian rhythms, which can also affect:

Symptoms of Disrupted Circadian Rhythms 

You’ll likely notice the disruption in circadian rhythms because of sleep problems. Symptoms of disrupted circadian rhythms may include:

  • Trouble falling asleep, staying asleep, or both
  • Excessive daytime sleepiness
  • Exhaustion, lethargy
  • Decreased alertness
  • Problems with memory and concentration
  • General aches and pains, stomach problems
  • Impaired judgment, risky behaviors

Causes of Disrupted Circadian Rhythms

Environmental factors, such as changes to the natural light-dark cycle, can push your internal clock out of sync. Causes for this include:

  • Too much exposure to light at night, including light from electronic devices
  • Shift work (a work schedule outside the hours of 7 a.m. and 6 p.m.), which goes against the natural light-dark cycle and alters your sleep pattern
  • Jet lag (the out-of-sync feeling when you travel through different time zones)
  • Shifting sleep habits or missing sleep, known as social jet lag
  • Chronic pain or other medical conditions
  • Mutations or changes in certain genes

Sleep Stages

To get a good night’s sleep, you must cycle through the four stages of sleep several times. They are:

  • Stage 1: During the short period at the start of light sleep called non-REM (non-rapid eye movement) sleep, your heartbeat, breathing, eye movements, and brain waves slow down. Your muscles relax and may occasionally twitch.
  • Stage 2: During the second stage of non-REM light sleep, your heartbeat and breathing slow down, your muscles relax, your body temperature drops, your eye movements stop, and your brain wave activity slows. 
  • Stage 3: During this third stage of non-REM sleep, you fall into a deep sleep that helps you feel rested in the morning. Your heartbeat, breathing, and brain waves slow to their lowest levels. Your muscles relax, and it’s harder to wake up. 
  • Stage 4: REM sleep (rapid eye movement sleep) occurs about 90 minutes after you fall asleep. Your breathing gets faster and irregular, your heart rate and blood pressure rise, and your arm and leg muscles are temporarily paralyzed. This is when you do most of your dreaming.

How to Reset Sleep Circadian Rhythms 

A circadian rhythm disorder happens when your internal clock and environment fall out of sync. This can cause sleep disorders that may lead to other health conditions, such as:

The amount of sleep you need changes throughout your lifetime and varies from person to person. In general, adults need seven to nine hours of sleep a night. If you have a sleep disorder, consider seeing a healthcare provider for a diagnosis.

A few ways to try to reset your circadian rhythms are:

  • Set a sleep schedule with regular sleep and wake times.
  • Wind down before bed by doing something restful and avoiding electronic devices.
  • Limit your exposure to light in the evening.
  • Clear the bedroom of light sources, including electronic devices.
  • Try to eat meals around the same time every day.
  • Avoid daytime naps.
  • Get regular exercise, but not too close to bedtime.
  • Limit caffeine, alcohol, and nicotine.
  • Try to get some sunlight during the day.

You can also try light therapy, which involves spending time each day in front of a light box. The goal is to adjust the melatonin in your body. To adjust earlier, you use the light box in the morning. You use it in the late afternoon or early evening to adjust later.

Melatonin and Sleep Aids

Some people use melatonin supplements to help reset circadian rhythms. Research suggests that melatonin may help with jet lag and some sleep disorders. Short-term use appears safe for most people, but there’s insufficient information on long-term safety.

Melatonin can cause side effects and interact with medications. Some brands may not have the amount of melatonin listed on the label.

Sleep aids, such as benzodiazepines and Ambien (zolpidem), may help you sleep better. There are also medicines, such as Prodigal (modafinil) and Nuvigil (armodafinil), that can help you stay alert. These medications can have side effects and may not be suitable for everyone.

Be sure to speak with a healthcare provider before taking dietary supplements or other sleep aids.

Are There Other Types of Circadian Rhythms?

Almost all living organisms are influenced by biological rhythms. Circadian rhythms may be the best known, but we have at least four different biological clocks, including:

  • Circadian: The 24-hour cycle of physical, mental, and behavioral rhythms
  • Diurnal: A circadian rhythm that synchronizes with the day/night cycle
  • Ultradian: Rhythms of shorter frequency, such as feeding cycles, blinking, and heart rate
  • Infradian: Rhythms with a cycle longer than 24 hours, such as menstruation or animal migration and hibernation

Summary 

Circadian rhythms, common to most living things, rise and fall in a 24-hour cycle. These rhythms are highly sensitive to environmental cues, such as light and dark, eating patterns, and physical activity. Our circadian rhythms tell us when to sleep and wake when all is well. And they play an important role in overall health.

Among the things that can throw the rhythm off are artificial light, jet lag, and shift work. You know there’s a disruption in your rhythm when you can’t sleep well at night and are sluggish during the day. Getting back in sync includes limiting artificial light, setting a sleep schedule, and getting some sunlight during the day.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Ann Pietrangelo

Ann Pietrangelo is a freelance writer, health reporter, and author of two books about her personal health experiences.

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