Good question. I believe I had my original nocturnal attacks because I was (and am) having health problems and I was worried something would happen and I wouldn't be able to care for my kids (I'm alone alot without my husband who travels). Now I've kind of trained myself to have them if I wake in the night, meaning I'm fearing the next attack so much that I'm causing it, I think. I hate to think that I'm doing that to myself, but it seems that the more you think about it, the more it happens.