I went through a period during my junior year in high school was I was constantly opiated for at least a few months, typically on 40 mg oxymorphones. I used to get sleep paralysis constantly in class or when I got home. I mean every day! Prior to the opiate use I had never experienced it whatsoever, so it freaked me out the first few times, but nothing major. There was on experience that REALLY sticks out in my memory, though. I was in chemistry, pretty much on the nod (come to think of it, I didn't even realize it, but I was on the nod most of my junior year). Anyway, I kept drifting into sleep paralysis and absolutely could not stop myself. But every single time, I would have an extremely vivid and realistic dream that the bell had rang, I was stuck in sleep paralysis, everyone in the class walked out, and I was stuck there unable to move. So I kept waking myself up because this underlying fear of getting caught all oped out was bugging me. I had the exact same dream/vision at least 10 times in a row and when the bell actually rang to get me out of class...well my mind was totally fucked. I really kinda thought I was stuck in like a permanent dream loop where I'd keep reliving the same moment forever and waking up. But I ended up fine.
Point of the story is, through later experimentation, I realized that a good dose of an opiate is very likely to cause me sleep paralysis, especially morphine. A 30 of morphine up the nose and I'm guaranteed to be in sleep paralysis within the day. Most other opiates don't seem to do this to me quite as much. I think certain people are just more likely to experience sleep paralysis than others, and for some reason opiates bring this on. Something to do with REM sleep and the sleep cycle I'm sure, but I'm too out of it to bother figuring out what exactly I mean or what exactly it is.
Point of the story is, through later experimentation, I realized that a good dose of an opiate is very likely to cause me sleep paralysis, especially morphine. A 30 of morphine up the nose and I'm guaranteed to be in sleep paralysis within the day. Most other opiates don't seem to do this to me quite as much. I think certain people are just more likely to experience sleep paralysis than others, and for some reason opiates bring this on. Something to do with REM sleep and the sleep cycle I'm sure, but I'm too out of it to bother figuring out what exactly I mean or what exactly it is.