Here's an interesting usenest post about this:
<i>In <3kdf8r$m8q@usenet.ucs.indiana.edu>
mlingwal@ucs.indiana.edu (Malinda
Jane Lingwall) writes:
>
>: Tim Beeman (Tbeeman@gladstone.uoregon.edu) wrote:
>: : This message may sound a bit odd but here goes. For about four
>: : years I have had something that i would call night paralysis. I wake
>: : up and I am concious but I can't move. It might last for a few seconds
>: : or a few minutes. Once I move part of my body, i will 'wake up'. Once
>: : awoken I tend to be breathing rather heavily and somewhat disturbed.
>: : It might happen 3 times in one night or once in a year. So that
>: : is that.
>: : About a year ago this paralysis happened about 4 times in one night.
>: : The final time I awoke and made a consious effort to not let it happen
>: : again. I fell back asleep and the next time i awoke it felt as though
>: : something was sitting on my back. It became hard to breath. I could
>: : only move my legs and arms. I thought I heard 'voices' laughing at me in
>: : the corner of my room. after some effort, i 'snapped out of it.'
>: : I have tried to research this in the library but haven't had much
>: : success. the only luck I have had was from a friend who had taken a
>: : folklore class. I was hoping someone out there could help me. I would
>: : appreciate it.
>: : Thank you,
>: : tim
>
> Since your friend had a folklore class, I assume he/she told you
>about the "Old Hag" phenomenon . . . its classic symptoms are paralysis,
>a feeling of being awake, a sense of someone being in the room, and
>an inability to breathe--like something is pressing on your chest.
>Actually, ppl who are being observed while they are experiencing this are
>said to be hyperventilating and, even though their eyes are often open,
>they are asleep. The old folktale is that an incubus or succubus (male
>or female demon) is attacking the person having the "dream". One theory
>listed in my folklore book is that it always occurs to ppl lying on their
>backs and is most likely caused by improper circulation. I can't really
>remember much more, but if you haven't looked up "Old Hag", that might be
>a place to start. I hope this helps you out!
>
> Malinda
>
>----------------------------------------------------------------------- -------
>Malinda Lingwall "Cyberspace . . . the final frontier. These are
>mlingwal@indiana.edu the voyages of the starship Emailprise."
>----------------------------------------------------------------------- -------
>
If you are interested in reading more about the "Old Hag" phenomenon,
you should order the following book from the University of Pennsylvania
Press, Blockley Hall, 418 Service Drive, Philadelphia, PA 19104-6097:
"The Terror That Comes in the Night: An Experience-Centered Study
of Supernatural Assault Traditions", David Hufford, University of
Pennsylvania Press, 1982 (ISBN 0-8122-1305-X).
The book is a detailed case study of this phenomenon. The author
reaches the following conclusions:
1. The phenomena associated with the "Old Hag" syndrome constitute
an experience with a complex and stable pattern, which is
recognizable and is distinct from other experiences.
2. This experience is found in a variety of cultural settings.
3. The pattern of the experience and its distribution appear
independent of the presence of explicit cultural models.
4. The experience itself has played a significant, though not
exclusive, role in the development of numerous traditions of
supernatural assault.
5. Cultural factors heavily determine the ways in which the
experience is described (or withheld) and interpreted.
6. The distribution of traditions about the experience, such as
those involving the Old hag or the Eskimo augumangia, has
frequently been confounded with the distribution of the
experience itself.
7. The frequency with which the experience occurs is surprisingly
high, with those who have had at least one recognizable attack
representing 15 percent or more of the general population.
8. The state in which this experience occurs is probably best
described as sleep paralysis with a particular kind of
hypnagogic hallucination.
9. Although there may be some connection between the etiology of
this experience and narcolepsy, and although certain illnesses
could be confused with the experience, the Old Hag experience
itself does not indicate the presence of any serious pathology.
10. The contents of this experience cannot be satisfactorily
explained on the basis of current knowledge.
-- Don</i>