"Studies have also shown links between heavy long-term use (over five joints daily over several years) and incidence of heart attacks, strokes, as well as abnormalities in the amygdala
regions of the brain."
marijuana (or tobacco, or anything else) can't be good for your heart: it's smoking.
I'd say you shouldn't worry especially if you don't smoke a lot.
It could be useful to check out this link: http://answers.yahoo.com/question/index?qid=20080425055959AARC1ym
One last thing: if you're worried about the effect on smoking marijuana on your body have you considered eating it instead? It's way cleaner, give it a try and see if it fits
you better. You can find lots of recipes on the internet.
@mindy n: THC
is not a "filler" it is the main psychoactive substance found in cannabis. Oregano could be a filler for instance.