I don't know, but another thing I occasionally suffer from is where I seem to nearly die while awake.
I went to a doctor's about it a while ago, and he recognised the symptoms, but couldn't find the name for what it was. I'd love to know what the name was. I actually had it happen to me again this morning, it's very scary and not much is known about it, apparently it's triggered by anxiety, but it's Boxing Day, I'm relaxing, I've no worries, I've just had Christmas, so I don't know why it happened this morning
Anyway, what happens is I sort of "wake up" from a dream, where I can see everything around me, but I can't move, or breathe. This usually lasts for about 5-10 seconds, but while it's happening it feels like a lifetime and is very frightening, because I can see everything, but I can't move or breathe. Apparently, my doctor told me what happens is that my brain is still half "asleep" and I awaken too soon, not giving my brain enough time to deliver the messages to my muscles to move/breathe etc. I am actually breathing, my diaphragm is moving up and down, but I can't feel it.
It only happens about 6 months apart, maybe more, but if I go back to sleep too soon after it happens, it happens again. It's the most frightening thing. If anyone recognises this and can supply me with any information on it, I'd love to know.