Circadian rhythm sleep disorders are a family of sleep disorders affecting the timing of sleep.
People with circadian rhythm sleep disorders are unable to sleep and wake at the times required for normal work, school, and social needs.
They are generally able to get enough sleep if allowed to sleep and wake at the times dictated by their body clocks.
Unless they have another sleep disorder, their sleep is of normal quality.
Humans have biological rhythms, known as circadian rhythms, which are controlled by a biological clock and work on a daily time scale.
Due to the circadian clock, sleepiness does not continuously increase as time passes.
Instead, the drive for sleep follows a cycle, and the body is ready for sleep and for wakefulness at different times of the day.