Short-term sleep deprivation usually causes little physical harm, since the body component for the lack of sleep by increasing its adrenaline levels during the day. A person may experience temporary feelings of pessimism or negativity. However, even short-term sleep deprivation can be dangerous if driving a car or operating machinery. Sleep deprivation is thought to cause half of all traffic fatalities. In fact, studies have shown that being forced to stay awake 17 to 19 hours can cause the same impaired abilities as having a 0.05 percent blood alcohol content.
