sleep is a basic biological necessity for all humans, indeed for all creatures on the planet. There is some natural variability and flexibility in the sleep cycle, hence people can go 24 or more hours without sleep in the right circumstances, without any lasting harm other than additional “rebound” sleep the next time they are able to sleep normally. However, if a person is deprived of sleep for longer than that, several mental and physical problems begin to develop.
The first signs of sleep deprivation are unpleasant feelings of fatigue, irritability, and difficulties concentrating. Then come problems with reading and speaking clearly, poor judgment, lower body temperature, and a considerable increase in appetite. If the deprivation continues, the worsening effects include disorientation, visual misperceptions, apathy, severe lethargy, and social withdrawal.