It came up in another thread but was off topic, so I thoughthttp://en.wikipedia.org/wiki/Sleep_paralysishttp://en.wikipedia.org/wiki/Night_terrorhttp://en.wikipedia.org/wiki/Hypnagogia
Here is my account written many years ago, I've not had anything similar happen since, although I have had the false awakenings:
I rarely have nightmares (a lot of my dreams are violent and disturbing but I'm rarely the victim!!) but the dream that scared me was a form of the Black Dog/hag/night terror/sleep paralysis which some people over the ages have interpreted as some kind of alien abduction/demonic attack (there was a very good program on it the other day). It only happened once but it left an impression.
I basically woke up to find a large Black Dog in the corner of my bed room (I have a largish Black Dog but this one was much larger and much more malevolent) but I was unable to move. In panic I woke up sweating with my heart pounding only to look over to the corner to find the Black Dog still there and I still couldn't move. I then woke up in panic and the dog had gone, I struggled out of bed but came over faint and collapsed on the floor only to wake up in panic in bed. This kept happening again and again Black Dog/fainting then waking in panic. Eventually I woke up to find the Black Dog was pinning me face down in the bed with its hands gripping my upper arms (it had changed into more of a Gigeresque Alien-type creature although I couldn't see its face - changing the whole thing into more of a Hag-like incident). I then kept waking and trying to escape and fainting and waking and being pinned by the Hag until I finally actually woke for real (heart pounding, soaked in sweat, actually out of breath) although it took a while for me to realise I was finally awake. I must have 'woken' about 15-20 times before actually coming around.
As an interesting footnote I found bruises on my upper arms where I was gripped by the Hag although the explanation is that one of my friends was giving me a few friendly punches in the pub or I was actually gripping my own arms in my sleep.
Although it was clearly a dream it has left me much more sympathetic to the claims of 'abductees' and it is clear that the experiences are part of a continuum. I certainly feel sorry for people who suffer from these kind of things on a regular basis and I could imagine such things would turn me into a basket case (esp. if it wasn't as obvious that it was a dream with the continual 'waking').
I have since heavily researched the topic on and off, over the years (I have a Future Shock bubbling under about it too), so if anyone is interested:
David Hufford's book The Terror That Comes in the Night An Experience-Centered Study of Supernatural Assault Traditions
is excellent, it is largely based on his research in Newfoundland but also looks at the wider issues. An aspect he brings out is that the locals have developed defences against the attack, and there are people with serious books offering defence techniques against alien abduction, some of which may work in similar ways:http://books.google.co.uk/books?id=Vl8HAAAACAAJSusan Clancy
's Abducted: How People Come to Believe They Were Kidnapped by Aliens
is more general and looks at how things like SP can be the basis for alien abduction accounts through the influence of hypnotherapy and pop culture. As I've said above it is a genuinely shocking experience* (one that appeared to also result in physical injuries, even if there is a different reason for those, I believe) and people searching for an explanation may find an abduction narrative works as an explanation for them, as attacks by supernatural creatures did in the past. Then again, it could be argued that as I was aware of SP this explanation fitted me experience and worked for me. Hmmmm.
* I now know someone who has them a lot and they are punishing and wearing even though she understands they are a form of parasomnia
Anyway enough about me, I'll throw this open to anyone who has been visited by the Night Mare or has found themselves Hag Ridden (and yes please, leave your jokes about the ex-wife at the door