Scientific explanation of sleep paralysis. The opposite of sleep walking. Not much research has been done on it, considered harmless. Estimated 8% of the population have sleep paralysis. I've had sleep paralysis and out-of-body projections since I was a child and never told anyone. Now my daughter tells me she is experiencing paralysis upon waking, hearing voices and being unable to speak or call out. Hereditary passed on neurodegenerative disorder or demons?