Sleep paralysis is a condition characterized by temporary paralysis of the body shortly after waking up (known as hypnopompic paralysis) or, less often, shortly before falling asleep.

More often than not, sleep paralysis is believed by the person affected by it to be no more than a dream

The hallucinatory element to sleep paralysis makes it even more likely that someone will interpret the experience as a dream, since completely fanciful, or dream-like, objects may appear in the room alongside one's normal vision.

Some scientists have proposed this condition as a theory for alien abductions and ghostly encounters.

What can be the reasons for such sleep paralysis?

Any suggestions?