Once told me that when you saw a homeless person who was talking to themself, and looking around without their wits, it was often because they lived in a constant state of sleep deprivation, and had effectively gone insane.

That comes somewhere from 3-14 days later. At that point you will have a hard time telling the difference between when you are sleeping and when you are awake. Somewhere between 21 and 30 days you will lose that ability. At this point you still are functional to some degree, but you will start to lose your sanity soon.