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A person who has a circadian rhythm disorder does not have a normal sleep-wake cycle. Their body tells them to stay awake and to sleep at times that do not conform to society’s norms.

People with circadian rhythm disorders may have less energy because their bodies are telling them that they are supposed to be asleep when society says they are supposed to be awake and alert.  This may cause others to perceive them as lazy. They may seek treatment for insomnia because they think they should be sleeping when their bodies are signaling them to stay awake. However, they will have no trouble falling asleep when it is their time to sleep.

If people with circadian rhythm disorders do not have the opportunity to sleep when they can, they can develop problems associated with sleep deprivation, such as tiredness, difficulty remembering things, difficulty concentrating and other health problems.  They can have trouble performing at school and at work and difficulty maintaining relationships, which can in turn lead to stress and depression.

alarm clock

Some people develop circadian rhythm disorders because of things that disrupt their sleep patterns. For example, if they travel across different time zones they may develop jet lag. If they work outside of what society would consider a normal shift, they may experience shift work sleep disorder.

However, some people with circadian rhythm disorders have not experienced any external disruptions to their sleep patterns. These people have intrinsic circadian rhythm disorders. Their circadian clocks are not aligned with those of most other people.

Everyone has a daily biological, or circadian clock. Activity in a part of the hypothalamus known as the suprachiasmatic nucleus (SCN) creates this clock. The SCN regulates body temperature, melatonin levels and cortisol levels, all of which affect energy and wakefulness/sleepiness.

Without any external cues, activity from the SCN would cause us to experience “days” of slightly more than 24 hours. However, light cues synchronize us to a 24-hour day. Our temperatures and our levels of melatonin and cortisol rise and fall at the same times in a 24-hour period. External cues that regulate our circadian rhythms are known as zeitgebers. In addition to light, zeitgebers can include meals and exercise.

When someone has an intrinsic circadian rhythm disorder, their cortisol and melatonin levels and their temperatures naturally rise and fall at unusual times. Intrinsic circadian rhythm disorders include delayed sleep phase syndrome (DSPS), advanced sleep phase syndrome (ASPD), non-24 hour sleep-wake syndrome, and irregular sleep wake disorder.

Light therapy, melatonin, medication, and exercise and naps at appropriate times can help people with circadian rhythm disorders modify their sleep cycles to be closer to the norm. However, some people with these disorders prefer to adjust their lifestyles to fit their biological clocks, for example, by working at night and sleep during the day.

Delayed Sleep Phase Syndrome

People with delayed sleep phase syndrome (DSPS) naturally fall asleep at least several hours later than society considers normal and wake up later than normal.  They usually fall sleep between 1 AM and 6AM and don’t wake up until late morning or the afternoon. DSPS affects mostly teenagers and young adults.  People with DSPS may believe they have insomnia because they can’t fall asleep early enough to be well rested for school or work the following day. They may try sleeping pills, but find that they don’t help them fall asleep and just make them feel more tired when they are supposed to stay awake.

However, if people with DSPS go to sleep when they feel sleepy and to stay awake when they feel alert, they will develop regular sleep patterns, and they will get enough sleep.

When people with DSPS are awake, they may feel exhausted, not just because their bodies are telling them that they should be sleeping, but because they are not getting enough sleep altogether.   Teenagers may perform poorly at school, and adults may perform poorly at work.  DSPS may be the reason why a teenager appears to be lazy or apathetic.

Advanced Sleep Phase Syndrome

Advanced sleep phase syndrome causes people to fall asleep and wake up earlier than society expects.  It usually affects middle-aged and elderly people, and its prevalence increases with age. People with ASPS may wake up as early as 2 AM and fall asleep as early as 6 PM.

People with ASPS may not have trouble functioning if they have jobs that allow them to get home before they start to feel sleepy.

Non-24 Hour Sleep-Wake Syndrome

Also known as free running sleep -wake syndrome, non-24 hour sleep wake syndrome causes the sleep-wake cycle to shift later each day. Someone with non-24 hour sleep wake syndrome ha s a circadian clock that is longer than 24 hours - usually 25 or 26 hours.

Sleep researchers think it is caused by the inability to respond to light cues. It affects the majority of blind people.

Non-24 hour sleep-wake syndrome is very difficult to live with because people who have it cannot maintain a regular schedule. Sometimes they will feel alert in the middle of the night and sleepy in the middle of the day, and sometimes they will feel sleepy in the middle of the night and alert in the middle of the day.

Irregular Sleep-Wake Syndrome

People with irregular sleep-wake syndrome (ISWS) fall asleep at least three times in every 24 hour period, at different times each day. They do not sleep more than four hours at a time. They get a healthy amount of sleep if they sleep when they are tired, but they will suffer from sleep deprivation if they force themselves to stay awake when they are sleepy.  ISWS is mostly associated with dementia in the elderly. However, it can occur in people of all ages who have had brain injuries or who have brain tumors as well as in children with autism.