Sleep-wake schedule disorder

Name(s): 
Inversion of sleep rhythm
Circadian dysrhythmia
Sleep disturbance
Sleep phase disorder
Nature 
The more common sleep phase disorder is delayed sleep phase, where sleep occurs later each day. In advanced sleep phase disorder, the tendency to sleep arrives earlier each day.
Incidence 
Researchers in the USA have shown that in the absence of an alarm clock people will sleep longer by up to two hours.
Aggravates 
Sleep deprivation [in 2 loops]
Type 
(G) Very specific problems