I've noticed it and a friend I introduced to it has noticed it too. I don't recall ever having a hangover from combustion but it's been a while and maybe it's just part of getting old? Idk figured I'd ask because I'm confused by it.
Yeah, if I hit it too hard at night and then go to bed without letting the effects wear off too much, then it will definitely mess with my sleep and make me feel groggy in the morning. Not as bad as a hangover, but still not great.