Sleep inversion or sleep-wake inversion is a reversal of sleep

Sleep

Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...

ing tendencies. Individuals suffering from sleep-wake inversion exchange diurnal habits for nocturnal habits, meaning they are active at night and sleep during the day. Sleep-wake inversion, when it is involuntary, can be a sign of a serious disorder.