Pain is an indicator of injury, but not always. Some things like sunburn initially don't hurt. It only starts to hurt when our skin cells begin to die.

A more dramatic example is radiation exposure. It doesn't hurt while a person is exposed because they can only feel what the sensory nervo...

People often get stressed about how much they should be sleeping. The stress elevates their cortisol that prevents them from sleeping. So they get into a vicious circle.

People who live in places where there is no electricity, iPhones or TV's don't sleep any more than the ...