Sleep paralysis occurs during the 5th (REM, dream) stage of sleep. Everyone who sleeps has sleep paralysis during this sleep stage.
"Another aspect of Stage 5 sleep is that the muscles in your arms and legs will go through periods of paralysis. Scientists speculate that this may be nature's way of protecting us from acting out our dreams.
The first period of REM sleep of the night usually begins about 90 minutes after you start drifting off, and lasts for about 10 minutes. As the night passes, the periods of REM sleep become longer, with the final episode lasting an hour or so." http://www.better-sleep-better-life.com/five-stages-of-sleep...
I don't understand why so many doctors and other experts are treating sleep paralysis as the problem. As someone who had frequent hypnagogic states, I can tell you that my problem wasn't sleep paralysis, it was my eyes opening during REM (dream stage) sleep. People often told me that I slept with my eyes (partially) open. Since most people here who've had this experience are either young, or were young at the time and stopped having the experiences, I'd assume it's something you usually outgrow. Rather than prescribing drugs, I suspect the best cure would be simply wearing a blindfold or blackout mask when sleeping.
I've had a couple of intense lucid dreams and it's not at all the same thing. During lucid dreams, I was in complete control and I was "somewhere else." During hypnagogic states, I had no control and was very much aware of being in my bed, paralyzed.
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