Circadian rhythm sleep disorders
| Circadian rhythm sleep disorder | |
|---|---|
| Classification and external resources | |
| Specialty | Psychiatry |
| ICD-10 | G47.2 |
| ICD-9-CM | 327.3, 780.55 |
| MeSH | D021081 |
Circadian rhythm sleep disorders (CRSD), a family of sleep disorders, affect (among other bodily processes) the timing of sleep. People with circadian rhythm sleep disorders are unable to go to sleep and awaken at the times commonly required for work and school as well as social needs. They are generally able to get enough sleep if allowed to sleep and wake at the times dictated by their "body clocks". The quality of their sleep is usually normal unless they also have another sleep disorder.
Humans, like most living organisms, have various biological rhythms. Circadian rhythms, often referred to as the body clock or the biological clock, control processes that re-occur daily, e.g. body temperature, alertness, and hormone secretion as well as sleep timing. Due to the circadian clock, sleepiness does not continuously increase throughout the day; a person's desire and ability to fall asleep is influenced both by the length of time since the person woke from an adequate sleep and by internal circadian rhythms. Thus, a person's body is ready for sleep and for wakefulness at relatively specific times of the day.
Sleep researcher Yaron Dagan states that "[t]hese disorders can lead to harmful psychological and functional difficulties and are often misdiagnosed and incorrectly treated due to the fact that doctors are unaware of their existence".
One of these disorders is extrinsic (from Latin extrinsecus, from without, on the outside) or circumstantial:
Formerly,jet lag, too, was classified as an extrinsic type circadian rhythm disorder.
Four of them are intrinsic (from Latin intrinsecus, on the inside, inwardly), "built-in":
Among people with healthy circadian clocks, there is a continuum of chronotypes from "larks", "morning people", who prefer to sleep and wake early, to "owls", "evening people" or "night people", who prefer to sleep late at night and wake at late times. Whether they are larks or owls, people with normal circadian systems:
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