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Sleep Disorders

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Faculty of Science, Mathematics and Engineering
Mental Health
The Mental Health Act (1983) | Insanity and the Law
Mood | Anxiety | Obsessions and Compulsions | Eating Disorders | Psychoses | Personality Disorders
Stress and Bereavement | Somatoform Disorders | Alcohol and Substance Misuse | Sleep Disorders | Obstetric
Child and Adolescent

It may seem odd to include sleep disorders in a series of entries on mental health, but sleep is both vital to mental well-being and reliant upon it. Mental illness and psychotropic medication can affect both how much and how well a person sleeps, and problems sleeping are in some cases treated with the sedatives. This entry takes a brief look at the sleep disorders, ranging from insomnia and narcolepsy to nightmares and sleepwalking.

The sleep disorders are broken up into secondary disorders, which are due to an underlying problem such as a medical condition, mental illness, or substance abuse, and primary disorders, where the problem is not due to a separate underlying cause. The primary disorders can be further split into dyssomnias and parasomnias. Dyssomnias involve a disruption of the quality, timing or quantity of sleep. They include insomnia, hypersomnia, narcolepsy, circadian rhythm disorders and sleep apnoea. Parasomnias occur during sleep and include nightmares, sleepwalking and night terrors.

Sleep Hygiene

Before looking at insomnia, it's worth going through the things that can be done to improve the chances of getting a good night's sleep. These are known collectively as 'sleep hygiene', and are all pretty much common sense:

  • The bedroom should be a dark, quiet place with a comfortable bed.

  • Stimulants (caffeine, nicotine, alcohol), exciting pastimes (television, video games), mobile phones, stressful matters, and large meals should all be avoided before bedtime.

  • Relaxing evening pastimes such as reading and hot baths can prove helpful, as can a hot chocolate or warm milk.

  • Sleep during the day should be avoided, and it is best to go to bed and wake at the same time every day.

  • The bed should only be used for sleep and sex  – this will help the brain associate the bed with sleep (or at any rate, something good).

  • Lying in bed awake for more than 15 minutes should be avoided by getting up and doing something relaxing. Do not use bedtime as a period for reflection upon your day unless you happen to be particularly happy about how it went.


Insomnia is a catch-all term for poor sleep, and as such has a number of different causes. In all secondary cases, treatment is of the underlying problem. In cases where an individual has had poor sleep for more than a month in the absence of an underlying condition, primary insomnia is diagnosed. This is often due to poor sleep hygiene, and so the treatment is simply the above advice. If this fails to help, sedative medications may help restore balance in the short term, but are highly addictive1 and are therefore only of limited use. In cases where the cause of the poor sleep remains a mystery, polysomnography may be used. This involves monitoring an individual's brain activity, eye movement, muscle movements, heart activity, blood oxygen levels, breathing, air entry rates and even snoring noises while they sleep.

Hypersomnia and Narcolepsy

Hypersomnia refers to a state of excessive sleepiness, leading to either an increase in time spent sleeping or episodes of sleep during the day. The Epworth Sleepiness Scale, which asks individuals to rate how likely they are to fall asleep in different situations, can be used to measure daytime sleepiness. Primary hypersomnia is diagnosed after a month of excessive sleepiness where no underlying condition is present, and is treated using stimulants such as methylphenidate or dexamphetamine.

Narcolepsy is a neurological condition in which an individual has attacks of sleep, often in unfortunate circumstances. These attacks last around 15 minutes and occur a few times each day. The condition can also produce hallucinations and sleep paralysis while falling asleep and waking, and cataplexy, a fleeting loss of muscle control following moments of shock or intense emotion. The condition may paradoxically produce insomnia during the night, leading to sleepiness during the day. Treatment is with scheduled naps throughout the day, with stimulants being used to treat sleepiness and tricyclic antidepressants being used to improve cataplexy and sleep paralysis.

Other Dysomnias

Circadian rhythm disorders occur when a person's environment does not match their internal circadian rhythm, leading to sleepiness during waking hours and wakefulness during sleeping hours. A good example is jet lag, in which travel between different time zones alters the day-night cycle without allowing the body a chance to keep up. Night shifts can produce a similar picture, and teenagers suffer chronically due to a combination of late night activities and lie-ins which reset the circadian rhythm to the point that they cannot wake up in the morning.

Sleep apnoea occurs when ventilation of the lungs is compromised during sleep, leading to poor quality sleep and daytime sleepiness. In obstructive sleep apnoea (OSA), obstruction of the upper airway leads to loud snoring with short episodes in which the individual stops breathing. The condition is more common in elderly and obese individuals, and those with Down's syndrome. Sleep apnoea may be confused with insomnia due to depression, and so it is important that others sleeping nearby are asked about the individual's sleeping habits. Treatment of sleep apnoea in children may involve removal of the adenoids, while weight loss, surgery and non-invasive ventilation via a face mask may be used in adults.


Sleepwalking, also known as somnambulism, tends to occur during deep sleep but may occasionally occur alongside dreaming. While there is no particular harm in guiding a sleepwalker towards a safe place, they are difficult to wake and will tend not to respond to attempts to communicate. Sleepwalking is most common around the age of twelve, and tends to run in families.

Nightmares are terrifying dreams that end in sudden wakening, following which the individual is fully awake and can recall details about the dream. They are most common in preschool children, but also affect some adults. Night terrors, on the other hand, involve a sudden awakening from deep sleep in a confused state, with no recollection of a dream or nightmare. On waking, the individual often screams and is sweaty with rapid breathing and a rapid pulse. Sleep terrors are thought to share an underlying cause with sleepwalking, and the two conditions often appear in the same families.

Please Note: h2g2 is not a definitive medical resource. If you have any health concerns you must always seek advice from your local GP. You can also visit NHS Direct or BBC Health Conditions.

1Benzodiazepines were used heavily at one stage during the 20th Century, meaning that, at the time of writing, a number of patients who were treated for sleeping problems decades ago are still dependent upon them.

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