Causes
The sopite syndrome has been associated with visually-induced and vestibular motion sickness. Other factors associated with drowsiness such as darkness or physical fatigue may intensify the effects of motion-induced sleepiness. The sopite syndrome may occur with little motional stimulus (though the greatest effects tend to be observed in subjects who have been exposed for longer periods of time), and often persists for a time after the motional stimulus has ceased.
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