I do this too. It isn't med related for me, at least I don't think it is. I've always done it. I think it's anxiety mostly. I do it whether asleep or awake. It has given me teeth and jaw problems. I cracked a molar and had to get a gold crown for it (not the kind that looks like a real tooth because I'll shatter it). I recently had the crown replaced because I'd worn a hole in it. The mouth guard I need is $800 and isn't covered by insurance. I've tried the over the counter ones, but they never fit right.