Sopite syndrome
Sopite syndrome is a poorly understood manifestation of motion sickness that causes drowsiness, mood changes, mental depression, and fatigue.[1] Sophite syndrome may be the cause of motion-induced sleepiness that is experienced in situations such as driving, flying and being on a boat. It is also believed to be why babies fall asleep when rocked.[2] Sopite syndrome has been linked to the vestibular system which may modulate the effects of motion that both causes ("rocking") and disturbs ("shaking awake") sleep.[3] Astronauts experiencing sopite syndrome have dubbed it "mental viscosity" or "the space stupids.".[4]