im one of those people that can have a panic attack/anxiety attack from smoking...even the increased heartrate.

i noticed it only happens on certain strains of weed (and it matters on how much i have).

theres been a strain or two that i can take 3 hits and possibly have a panic attack...then there are others i can twist up a blunt and smoke it to myself without the slightest ill-effect.

I noticed i feel best of certain headhigh sativas. im a pretty stressed person to begin with most of the time (although i appear laid back my mind is always running in 10 different directions) so when i have certain weeds that make me feel paranoid or not in control of my body then it makes me breathe really fast but i dont notice it when its starting...so yea...i passed out once from that...hit my head...not fun...

but like i said i think it matters on the strain...some dont bother me at all and other makes me uncomfortable.

usually though i always get the uncomfortable feeling with all high thc content indicas (18% and up) but it usually goes away within 10 mins of me feeling the effects of the weed.