Sleep Disorders – What are they?

Naomi Carr
Author: Naomi Carr Medical Reviewer: Dr. Brittany Ferri, PhD Last updated:

Sleep disorders are a collection of medical conditions that impact the quality, quantity, and length of sleep. They can cause or exacerbate several physical and mental health conditions, cause impairments in cognitive functioning, and create dangers for the person affected [1].

Types of sleep disorder

Some of the most common or most disruptive sleep disorders are as follows:


Insomnia is the most common sleep disorder, with around a third of all adults experiencing short- or long-lasting insomnia at some point in their lives [2]. Long-term or chronic insomnia is diagnosed when symptoms have persisted for at least three months, occurring three or more times per week.

Symptoms of insomnia include [3]:

  • Difficulty falling asleep, potentially lying awake in bed for a long time
  • Frequently waking in the night or being asleep for a short period of time and then waking
  • Waking up very early
  • Feeling very tired during the day
  • Cognitive impairment, including trouble concentrating or remembering
  • Mood and behavior changes, including anxiety, depression, irritability, or aggression

Sleep apnea

There are two types of sleep apnea; obstructive sleep apnea, caused by a blocked airway, and central sleep apnea, caused by a reduction in brain signals that are required to breathe.

Symptoms of sleep apnea include [4]:

  • Breathing that stops and starts during sleep
  • Gasping for air while asleep
  • Loud snoring
  • Frequently waking up during the night
  • Cognitive impairment, including trouble concentrating or remembering
  • Mood and behavior changes
  • Daytime sleepiness
  • Headaches


Symptoms of narcolepsy include [5]:

  • Frequently waking up during the night
  • Hallucinations or paralysis when falling asleep or waking up
  • Feeling excessively tired during the day
  • Suddenly falling asleep in the daytime, sometimes for just a few seconds or minutes
  • Sudden muscle weakness, such as feeling your knees buckle beneath you, also known as cataplexy

Restless legs syndrome

Symptoms of restless leg syndrome include [6]

  • Uncomfortable, and sometimes painful, sensations in one or both legs, causing a feeling that you must move or twitch your leg
  • Worsening symptoms at night, while resting, or sitting still for a long time
  • Trouble falling asleep because of these sensations
  • Feeling sleepy in the day
  • Impaired cognition, including difficulty concentrating
  • You may also experience periodic limb movementdisorder, symptoms of which include regular and repeated movements in the legs while asleep, including cramping, twitching, or bending, up to or over 15 times per hour [7]

Non-24-hour sleep wake disorder

The circadian rhythm, or sleep-wake cycle, is actually slightly over 24 hours, but with environmental, social, and natural cues, we typically are able to maintain a 24-hour cycle. However, some people are unable to utilize these cues to regulate their circadian rhythm (most often due to total blindness, although it can occur in the sighted), causing a non-24-hour sleep wake disorder, also known as circadian rhythm disorder.

Symptoms of non-24-hour sleep wake disorder include [8]:

  • Times of sleeping, waking, and eating being pushed slightly later and later each day
  • Sleeping during the day and struggling to sleep at night
  • Impaired ability to concentrate at work or school
  • Inability to stick to a structured schedule, potentially causing social, professional, or emotional problems
  • Eventually catching up to normal sleep and wake times after several weeks, for a short period of time, before recommencing a shifting schedule

Shift work disorder

Shift work disorder occurs in those who work shifts during the night or early morning, between 7pm and 6am, disrupting the circadian rhythm.

Symptoms of shift work disorder include [9]:

  • Difficulty sleeping between shifts, as this is usually in the daytime
  • Feeling very sleepy at work, particularly in the middle of the night
  • Increase in errors and accidents
  • Difficulty concentrating


Parasomnia is the collective name of several unusual behaviors that occur during the various stages of sleep and impact sleep quality [10]. Many of these experiences can be very frightening or concerning.

Parasomnias that can occur during non-rapid eye movement (NREM) sleep, when sleep is shallow, include:

  • Sleepwalking (somnambulism): walking or performing actions or tasks with open eyes, but while being only partially awake and not aware of the surrounding environment, then not being aware of these actions once awake
  • Night terrors: sitting up in bed and screaming, sometimes running in fear
  • Confusion arousal: briefly talking or doing something without any awareness of actions or environment

Parasomnias that can occur during rapid eye movement (REM) sleep, or deep sleep, include:

  • REM sleep behavior disorder: vivid and scary dreams, sometimes including movements that act out behaviors in the dream, such as running away or fighting off attackers, most of which can be recalled upon waking
  • Sleep paralysis: becoming conscious during a period of REM sleep, while the body remains atonic as though still asleep, causing an inability to move, sometimes for several minutes, and occasionally accompanied by hallucinations of someone in the room or sitting on the chest
  • Nightmare disorder: recurrent vivid nightmares, often involving dangers and fighting for survival, and events that cause a great deal of anxiety upon awakening

Parasomnias that can occur in the time between being asleep and being fully awake include:

  • Exploding head syndrome:hearing a loud bang or seeing a flash, which is painless, but can be concerning or frightening
  • Sleep enuresis:uncontrollable bedwetting
  • Sleep-related hallucinations:seeing, hearing, or feeling something that is not there, sometimes for several minutes

Common causes of sleep disorders


Research suggests that most sleep disorders are genetic, with increased risks in those with a family member who has been diagnosed with a sleep disorder [3][4][6][10].

Brain functioning

Several studies suggest that the way in which the brain works can impact sleep, including changes in signals being sent to the body [4], changes or deficiencies in neurotransmitters, particularly dopamine [6], and an impaired ability for the brain to regulate the circadian rhythm [8].


Stress and anxiety related to work, family, relationships, illnesses, or life changes, can greatly impact sleep quality and quantity [2][7][10].

Pregnancy and childbirth

Disturbed sleep has been found to be common during pregnancy, particularly the third trimester, and within the first four weeks following childbirth.

This could be due to extreme hormone changes, particularly progesterone, which impacts melatonin and sleep; changes in lifestyle while caring for a newborn baby; postpartum depression or mood changes; or changes in weight [11].

Menstrual cycle

Hormone levels fluctuate during the menstrual cycle and many women experience premenstrual symptoms (PMS) prior to their period caused by these hormone changes, which can impact sleep as melatonin levels can be altered. Similarly, mood changes within this time can also impact sleep, such as feelings of anxiety or depression [12].


As people age, their risk of experiencing sleep disorders increases [1]. This applies to most sleep disorders, although certain disturbances, especially various parasomnias, occur more often in children and can reduce with age [10].


Working shifts, regularly traveling, and experiencing regular noise disturbances during the night can all increase the risk of experiencing a sleep disorder.


The risk of sleep disorders is increased in those who don’t engage in any exercise, are obese, smoke cigarettes, take illicit substances, or drink a lot of caffeine or alcohol [3][4][6].

How are sleep disorders diagnosed?

Initially, your doctor will conduct physical health checks such as blood tests, gather a medical history of any mental or physical health conditions experienced by you or your family members, and ask for information on any medications you are currently taking [1].

There may be an underlying physical or mental health condition that is impacting your sleep, such as an iron deficiency, diabetes, anxiety, or depression. If so, your doctor will aim to treat this condition first, which could reduce your issues with sleep.

They will ask questions about your sleep, such as what disturbances you are experiencing, how often they occur, and how they are affecting your life and functioning. They will ask about your caffeine and alcohol intake, lifestyle, and schedule.

They may ask you to complete a sleep diary, to get a clearer picture of your sleep patterns, disturbances, and symptoms [3][4].

After gathering this information, your doctor may be able to make a diagnosis, based on which they will recommend a treatment plan.

However, they may require further information, so might suggest that you take part in a sleep study. This could take place at your home or in a specialized place and will involve monitoring your sleep for a length of time, while potentially monitoring brain changes and physical symptoms, to better understand your condition [1][2].

How are sleep disorders treated?


Engaging in therapy, particularly cognitive behavioral therapy (CBT), may help to reduce your feelings of anxiety or stress, help you form better sleep hygiene, or manage and change your negative beliefs around sleep. Developing more positive feelings or behaviors around sleep could reduce your symptoms [3][10].

Light therapy

Light therapy involves the use of a specifically designed light box. This can help reset your circadian rhythm by affecting the release of brain chemicals, particularly melatonin and serotonin, which regulate sleep [3].

Sunlight reduces the release of melatonin, causing us to feel more awake, while darkness prompts the release of melatonin, causing us to feel sleepy, so with the use of the light box, you can help to create these effects and improve your sleep-wake cycle [8].


Your doctor may prescribe medication to help reduce the symptoms of your sleep disorder.

To help you go to sleep, they may prescribe melatonin supplements, antihistamines with a sedative effect, or a short-term course of benzodiazepines [3].

To help you stay awake, you may be prescribed an amphetamine medication, such as methylphenidate [5].

To prevent unwanted movements during sleep, you may be prescribed an anti-seizure medication, such as gabapentin [6][7].

It is important that you take your medication exactly as prescribed by your doctor, as taking too much, missing doses, or suddenly stopping a medication can cause serious adverse effects.

Breathing devices

For sleep apnea or other breathing-related sleep disturbances, your doctor may recommend a breathing device, such as a continuous positive airway pressure (CPAP) machine [4].


You can do several things to improve your sleep quality and reduce symptoms of sleep disorders, including:

  • maintaining a regularsleep schedule and waking at the same time each day
  • come up with a bedtime routine to help ready yourself for sleep
  • ensuring your room is dark and quiet at bedtime
  • avoiding caffeine and alcohol before bed
  • avoiding electronic screens before bed
  • engaging in regular exercise
  • going outside in the morning sunlight
  • utilizing relaxation techniques such as meditation or breathing exercises

The importance of sleep

Ensuring you get enough sleep is vital to your physical and mental well-being, as it has several functions in the development, protection, and restoration of the body and mind [13].

Inadequate amounts or quality of sleep can cause increased risks of:

  • Cardiac issues, such as heart attack and high blood pressure
  • Stroke
  • Changes in metabolism, potentially leading to obesity and diabetes
  • Hormonal imbalance
  • Impaired immune system
  • Cognitive impairments, such as decrease in concentration and memory
  • Mood changes, including depression and anxiety
  • Behavioral changes, including agitation, aggression, and hyperactivity
  1. National Library of Medicine. (Updated 2020). Sleep Disorders.MedlinePlus. Retrieved from
  2. Roth, T. (2007). Insomnia: Definition, Prevalence, Etiology, and Consequences. Journal of Clinical Sleep Medicine: JCSM: Official Publication of the American Academy of Sleep Medicine, 3(5 Suppl), S7–S10. Retrieved from
  3. National Heart Lung and Blood Institute. (Updated 2022). Insomnia. NIH. Retrieved from
  4. National Heart Lung and Blood Institute. (Updated 2022). Sleep Apnea. NIH. Retrieved from
  5. National Institute of Neurological Disorders and Stroke. (Reviewed 2022). Narcolepsy.NIH. Retrieved from
  6. National Institute of Neurological Disorders and Stroke. (2017). Restless Leg Syndrome.NIH. Retrieved from
  7. Joseph, V., & Nagalli, S. (2022). Periodic Limb Movement Disorder. In StatPearls [Internet], Treasure Island, FL: StatPearls Publishing. Retrieved from
  8. Quera Salva, M.A., Hartley, S., Léger, D., & Dauvilliers, Y.A. (2017). Non-24-Hour Sleep-Wake Rhythm Disorder in the Totally Blind: Diagnosis and Management. Frontiers in Neurology, 8, 686. Retrieved from
  9. Wickwire, E.M., Geiger-Brown, J., Scharf, S.M., & Drake, C.L. (2017). Shift Work and Shift Work Sleep Disorder: Clinical and Organizational Perspectives. Chest, 151(5), 1156–1172. Retrieved from
  10. Fleetham, J.A., & Fleming, J.A. (2014). Parasomnias. CMAJ: Canadian Medical Association Journal, 186(8), E273–E280. Retrieved from
  11. Silvestri, R., & Aricò, I. (2019). Sleep Disorders in Pregnancy. Sleep Science (Sao Paulo, Brazil), 12(3), 232–239. Retrieved from
  12. Baker, F.C., & Lee, K.A. (2018). Menstrual Cycle Effects on Sleep. Sleep Medicine Clinics, 13(3), 283–294. Retrieved from
  13. National Heart Lung and Blood Institute. (Updated 2022). How Sleep Works. NIH. Retrieved from
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Naomi Carr
Author Naomi Carr Writer

Naomi Carr is a writer with a background in English Literature from Oxford Brookes University.

Published: Dec 22nd 2022, Last edited: Sep 22nd 2023

Brittany Ferri
Medical Reviewer Dr. Brittany Ferri, PhD OTR/L

Dr. Brittany Ferri, PhD, is a medical reviewer and subject matter expert in behavioral health, pediatrics, and telehealth.

Content reviewed by a medical professional. Last reviewed: Dec 22nd 2022
Medical Reviewer Medical Reviewer:
Brittany Ferri
Last reviewed: Dec 22nd 2022 Dr. Brittany Ferri, PhD