Have you ever wondered why human beings tend to sleep at night and work during the day? With exceptions aside, that’s how almost everyone functions. Lack of sleep makes us cranky throughout the day. Why does that happen? It's all related to our biological master clock or circadian rhythm. What is Circadian Rhythm?  The circadian cycle refers to the metabolic changes that occur within a living organism over 24 hours. The term ‘Circadian’ comes from two Latin words Circa meaning around and Diem meaning day.  Circadian rhythm is a natural, internal process that regulates the sleep-wake cycle and repeats roughly every 24 hours. This rhythm is influenced by external cues such as light and temperature along with internal factors including genetics and hormones. Read more: What is Autism spectrum disorder? Why is Autism Awareness Important? How Does Circadian Rhythm Work?  Just like a master clock regulates the time zone across the world, there’s also a master clock in the human body that regulates sleep patterns and sense of time. It's situated in the hypothalamus of the brain, specifically in an area called the suprachiasmatic nucleus (SCN).  The SCN receives input from the eyes, particularly light-sensitive cells in the retina, which helps synchronize the internal clock with the external day-night cycle. The circadian rhythm regulates the sleep-wake cycle by controlling the time alertness of the human body through melatonin production. Additionally, it also plays a significant role in body temperature regulation.  Circadian rhythm disorder is generally caused due to genetic factors, erratic light exposure, medical conditions, age-related changes, psychological stress, etc. Read more: Cerebral Haemorrhage: Signs, Reasons, Treatment, and Prevention Symptoms of Circadian Rhythm Disorder  There are several symptoms of circadian rhythm disorder. The common ones include:  Insomnia The most common symptom of circadian rhythm disorder is difficulty with sleep or insomnia. A patient gradually develops difficulty in either falling asleep or staying asleep. Waking up multiple times at night is also attributed to this disorder.  Increased Daytime Sleep A decrease in sleep quality results in increased daytime sleepiness. This symptom is directly related to sleep difficulty as waking up multiple times during the night results in drowsiness throughout the day.  Early Wakeup  At a more advanced stage, a person might find it difficult to fall asleep after waking up during the night. Sleep deprivation triggers fatigue which inherently harms other body processes.  Read more: Why are Suicide Rates Higher Among Men? Concentration Difficulty  People with circadian rhythm disorder may find it difficult to concentrate or face memory-related problems. The lack of balanced sleep affects certain cognitive functions of the brain and affects decision-making capabilities.  Mood Swings  Circadian rhythm disorder may trigger severe mood swings. It increases the risk of depression and anxiety leading to BPD at later stages.  Besides, physical symptoms like headaches and gastrointestinal issues may be caused by the disorder.  Read more: Self-care Tips for Parents of Newborns Types of Circadian Rhythm Disorder  The difference in sleep-wake cycle characteristics resulted in several types of circadian rhythm disorders. The prominent ones are:  Delayed Sleep Phase Disorder  Delayed Sleep Phase Disorder of DSPD is the most common type of this disorder. A person with DSPD has a convoluted biological clock which makes it difficult for them to sleep at conventional bedtimes.  As the name suggests, DSPD delays the conventional sleeping time by several hours. The subsequent result is sleepiness continued well into the day.  Advanced Sleep Phase Disorder  ASPD is the opposite of DSPD. In this case, an individual might experience a sleep cycle well in advance compared to the conventional sleeping times.  Irregular Sleep-Wake Rhythm Disorder Irregular sleep-wake rhythm disorder is usually triggered by insomnia or fragmented sleeping patterns. Waking up multiple times during a sleep cycle may induce an irregular disorder.  Read more: 7 Types of Strength Training And Their Benefits Shift Work Sleep Disorder Shift work sleep disorder is seen among people with unconventional work hours. For example, a person working night shifts may find it difficult to sleep during the day. The result is sleepiness and drowsiness in the subsequent work shifts at night.  Non-24-Hour Sleep-Wake Disorder Non-24-hour sleep-wake Disorder is usually noticed among individuals with complete blindness. The lack of light perception makes the brain lose perception of the light-dark cycle in 24 hours. As a result, affected individuals experience a gradual shift in their sleep-wake schedule, leading to periods of insomnia and excessive daytime sleepiness. Jet Lag Disorder Jet lag disorder is seen among individuals who travel between several time zones. Unlike the other types, jet lag disorder usually improves once the body gets adjusted to the new timezone. However initial symptoms may include sleeplessness, digestive issues, and reduced cognitive functions.  Read more: Colon Cancer: Everything You Need to Know How to Reset the Circadian Rhythm Circadian rhythm can be restored through certain lifestyle changes. In addition, behavioral strategies, and sometimes medical interventions may be needed to improve the condition. Here are some strategies to get started.  Practicing a Consistent Sleep Schedule  One of the best ways to reset the circadian rhythm is to maintain a strong routine. It is recommended to go to bed and wake up at a fixed time every day, even on weekends. This would allow your body to get used to a consistent cycle and adjust accordingly.  Light Exposure  Circadian rhythm is greatly regulated by light and dark. Try and increase your light exposure when you wake up in the morning. Go for a short walk or spend some time on the balcony. The more you’re exposed to natural light in the morning, the more the body adjusts to the wake period.  Read more: How Does Physical Activity and Exercise Affect Testosterone Levels? Limit Night Time Exposure  Just as the opposite of morning, limit the light exposure at night. It is advised to avoid the use of blue light emitting sources like TV and mobile late at night. This will help in the production of melatonin which will naturally induce sleep.  Create a Relaxing Environment  Avoid stressful work during the night if possible. Create a relaxing environment by listening to slow music, reading a book, taking a shower, or practicing meditation to ease brain functions.  Avoid Day Naps  It can be helpful to avoid naps during the day. If you can’t entirely avoid them, try and limit naps to no more than 30 minutes. Long naps during the day will interfere with nighttime sleep.  Read more: Measles: Causes, Symptoms and Prevention Avoid Stimulating Substances  It is recommended to avoid stimulating substances like coffee, tea, or nicotine before sleep. It might trigger hyperactivity in the brain which will deter the usual sleeping time.  Consult a Healthcare Professional If the disorder persists, consult a healthcare professional. A trained medical practitioner can provide personalized treatment for the disorder.   Final Words  The circadian rhythm or biological clock ensures a healthy sleep-wake cycle in the human body. When this rhythm goes off balance it may result in several complications in physical and emotional health. Fortunately, it is possible to reset the circadian rhythm without medical intervention unless in extreme cases. Make sure to lead a routined and disciplined lifestyle including a timely sleep schedule to maintain a healthy rhythm.  Read more: How Does Fat Leave the Body When We Lose Weight?