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Sleep Disorders

Sleep-related complaints are second only to complaints of pain as a cause to seek medical attention. Unfortunately, they’re more common than ever. According to the CDC, more than a third of American adults don’t get enough sleep on a regular basis.

Many sleep disorders are related to or caused by another underlying condition, such as anxiety or depression. Some people are born with them. Some develop simply from poor sleep hygiene, such as not following a regular schedule or using electronics late at night.

At Tuck, we classify sleep disorders into six major categories based on the International Classification of Sleep Disorders: Insomnias, Circadian Rhythm Sleep-Wake Disorders, Hypersomnias, Parasomnias, Sleep-Related Movement Disorders, and Sleep-Related Breathing Disorders.

Keep reading to learn more about sleep disorders, how they’re diagnosed, and the risks they pose when left untreated.


Insomnia describes a general difficulty falling or staying asleep. It’s one of the most common sleep disorders.

After just one night of short sleep, individuals experience the effects of sleep deprivation the following day, which include difficulty focusing, irritability, impulsivity, and lack of balance. When people have insomnia, they get short sleep on a more regular basis. As a result, the symptoms of sleep deprivation persist for a period of days to years. These symptoms are disruptive to all aspects of daily life, and worsen with time.

On a cognitive level, the sleep deprivation caused by insomnia can negatively impact school or work performance, and increase one’s risk of Alzheimer’s. From an emotional health perspective, the severe mood changes and lack of motivation may develop into depression and substance abuse. Finally, chronic sleep deprivation has been linked to serious physical health problems like obesity, diabetes, and cardiovascular disease.

Short-term, occasional insomnia lasts anywhere from a few days to a few months. It affects about one in five people. When these symptoms persist for a period of six months or more, it’s diagnosed as chronic insomnia. Chronic insomnia affects 10% of adults.

Sometimes, insomnia results from a lack of good sleep hygiene. In these cases, fixing the insomnia is as simple as making a few lifestyle changes, like exercising earlier in the day and avoiding caffeine and electronic devices at night.

More often, insomnia is actually a symptom of another, comorbid condition, like a mental health disorder, chronic health issue, or even another sleep disorder. In these cases, treating the underlying condition often results in improved sleep. The insomnia may also be directly treated using a combination of cognitive-behavioral therapy, lifestyle changes, and sleep aids.

Circadian Rhythm Sleep-Wake Disorders

Circadian rhythm disorders affect people who have a circadian rhythm—or sleep-wake cycle—that is out of alignment with what’s normal. A healthy circadian rhythm roughly follows the patterns of the sun: we wake up in the morning as the sun rises, begin to tire as it falls in the evening, and fall asleep once it’s gone at night.

Your circadian rhythm dictates much more than your sleep patterns, including your hormone levels, body temperature, and appetite. As a result, when people have an abnormal circadian rhythm, it disrupts their quality of life. They have trouble waking up and falling asleep at “normal” times, don’t feel energized at the same time others do, and generally have difficulty concentrating during the day.

The most common example of a circadian rhythm disorder is jet lag, which occurs when a person travels rapidly to another time zone where the patterns of sunlight mismatch those from where they came. Jet lag often goes away in a few days, though. Living with a circadian rhythm disorder is like having permanent jet lag.

Circadian rhythm disorders can stem from lifestyle causes, such as with shift-work sleep disorder (where the person gets less access to natural sunlight as a result of working the night shift). The person may also be born with it, as can happen with blind or visually impaired people. Since they have trouble perceiving light, they’re often more prone to non-24 hour sleep-wake disorder.

Circadian rhythm disorders are typically treated using a combination of melatonin and light therapy, where the individual sits in front of a specialized light box for a set period of time each day, in order to reset their circadian cycle.


In simple terms, hypersomnia is the opposite of insomnia. Unlike individuals with insomnia, who have difficulty getting enough sleep, people with hypersomnias sleep longer than “normal,” usually 9 hours or more, and yet they still don’t feel adequately rested upon waking up. They often have difficulty waking up in the morning and feel groggy throughout the day.

The excessive daytime sleepiness associated with hypersomnia can also be a symptom of another sleeping disorder (like sleep apnea). However, idiopathic hypersomnia is distinct from other sleep disorders in that the sleepiness persists, independently of a circadian rhythm issue or environmental nighttime disturbance. Doctors do not yet know what causes idiopathic hypersomnia.

Narcolepsy is another form of hypersomnia. This rare, lifelong hypersomnia has two distinct types. Both are characterized by excessive daytime sleepiness, but one also includes symptoms of sudden sleep attacks during the day, sleep hallucinations, and sleep paralysis. Narcolepsy is a neurological disorder caused abnormalities in the brain, but no cure yet exists.

Often, patients with narcolepsy are prescribed drugs like Ritalin and SSRIs to help manage their symptoms. Patients with other hypersomnias may also use stimulants to manage their disorder, along with cognitive-behavioral therapy, light therapy, and lifestyle changes.


Parasomnias describe abnormal behaviors that take place during the transition between the various sleep stages. Typically, these occur during the transition from wake to sleep, sleep to wake, and between nREM and REM sleep. Common parasomnias include:

  • REM Behavior Disorder, where the individual moves or yells violently during REM sleep
  • Sleep paralysis, where the individual feels alert but unable to move when they are falling asleep or waking up
  • Sleepwalking, where the person may stand up and walk around during NREM sleep, often in the first half of the night
  • Exploding Head Syndrome, where the individual hears a sudden, loud noise that jolts them awake just as they are falling asleep or waking up
  • Night terrors, where the individual suddenly sits up, screams, or appears panicked, during the transition between NREM and REM sleep

Sleep experts estimate that most adults (66%) will experience a parasomnia at some point in their lives. Some parasomnias, such as bedwetting and sleepwalking, are more prevalent during childhood, with many children growing out of them by adolescence. Others can persist throughout life, such as REM behavior disorder. Still others may happen more occasionally, such as exploding head syndrome and sleep paralysis.

Part of what makes diagnosing these types of sleep disorders tricky is that the individual experiencing them often doesn’t remember the event. Typically, another person in the household is the one who notices the symptoms.

Sleep-related movement disorders describe any abnormal movements that occur during sleep, or in the transition from wake to sleep. Common sleep movement disorders include:

  • Sleep bruxism, which is characterized by unconscious, involuntary grinding of the teeth during sleep
  • Restless leg syndrome (RLS), which is characterized by an uncomfortable, “pins and needles” sensation in the lower limbs that occurs when the person is lying down, and can only be relieved by moving the legs
  • Periodic limb movement disorder (PLMD), which is characterized by repetitive leg movements during nREM sleep, often unbeknownst to the individual

Sleep-related movement disorders are problematic because they result in sleep deprivation. Since RLS acts up when the person is lying down, it makes it difficult for them to fall asleep, leading to insomnia. Other sleep movement disorders, like bruxism and PLMD, disrupt the person’s quality of sleep through movement, likewise contributing to sleep deprivation. Sleep bruxism can also cause permanent teeth damage, if left untreated.

Sleep movement disorders are rarer than other types of sleep disorders, occurring in 4% to 10% of adults, although certain groups are at increased risk, such as those over age 65 or pregnant women (for RLS in particular). They often go undiagnosed, since they occur when the person is unconscious, and the symptoms pop up in indirect ways. For instance, an individual with sleep bruxism may experience morning headaches and jaw pain.

Treatment usually includes sleep products like weighted blankets and dental devices, and behavioral changes like avoiding caffeine and alcohol. Psychotherapy can also be helpful, since stress often contributes to or worsens sleep bruxism.

Sleep-related breathing disorders describe any abnormal breathing, pauses in breathing, or difficulty in breathing during sleep. Chronic snoring and sleep apnea are the two most common sleep breathing disorders.

Chronic snoring may not seem like such a big deal, but it is often a symptom of the much more serious sleep apnea. Sleep apnea occurs when the individual literally stops breathing during sleep. This is called an “apnea.” In order to start breathing again, the brain has to momentarily wake up, even if the person remains unconscious. This disruption interferes with the person’s quality of sleep, and their progression through the sleep cycles, often preventing them from getting the REM sleep they need.

What makes these disorders difficult to diagnose is that the individual often does not know they are happening. They may be getting sufficient amounts of sleep each night, yet they feel tired the next day. Often, someone finds out they have a sleep breathing disorder because someone alerts them to it—such as the bed partner they keep waking up at night with their loud snores.

Sleep-related breathing disorders should be taken seriously. Anywhere from 18 to 22 million Americans have sleep apnea, with a large number of cases going undiagnosed. They cause sleep deprivation, which contributes to cognitive decline and impaired daytime focus, and has been linked to physical conditions like diabetes and heart disease. More concerning, sleep breathing disorders can cause life-threatening conditions wholly independent of sleep problems—like low blood oxygen levels, high blood pressure, heart attacks, and stroke.

The Risks and Dangers of Sleep Disorders

Sleep disorders are ubiquitous, and the government estimates 25%-30% of adults in the US have a disorder that results in some impact on mortality and disability.

The most common comorbidities that go along with insomnia are psychiatric. The association between sleep problems and mental illness are manifold, and most psychiatric illnesses show insomnia or hypersomnia as a symptom.  Researchers have elucidated that unhealthy beliefs about sleep can raise the risk for suicide, as can, in some cases, nightmares.  Unhealthy beliefs include the idea that sleep disturbances cannot be relieved or overcome.