i think that getting dizzy/ headrush more often while high can be explained by urgency. sure if you arent high it can still happen, but when you are high you are on the couch or whatever, and really hungry. theres a breaking point where "need munchies NOW" overcomes "im so high i dont want to get up" and it has to be enacted quickly before "too high to move" takes over again. so you stand up with incredible speed, and then fall on your face from the blood draining to your feet. can be avoided (those times you want to smoke silly) by making your munchy food first then not moving from your spot. if you do have to move, take the time to get up a little at a time, deep breaths and all that.