Usually when we think of the side effects of marijuana we think, munchies! And long term side effects, maybe some psychological disorders, which aren’t yet proven. But a new study shows that heavy marijuana use may increase your risks of heart attack, heart disease and stroke. The levels of a protein called apolipoprotien C-III in long term marijuana users are found to be 30% higher. This protein is involved with a type of fat found in the blood, and higher levels of the protein makes higher levels of that fat. This can contribute to hardening of the arteries or thickening of the artery walls.
But the tests they ran were on users that averaged smoking 78-350 joints per week. Anything in excess can cause great damage, whether this marijuana, alcohol, or even lettuce.

That's a good point.  It seems like they never want to do studies on moderate marijuana use.  350 joints per week is absolutely ridiculous, that only accounts for about 99.9% of marijuana users.  Most people who smoke pot, do it moderately, 5 joints a day is unreal.