Hahaha oh wow.
There is no proof that marijuana is actually harmful.
Uh.
Yes there is are you completely stupid or what.
1. It's extremley adictive, not having it after having some makes you grumpy and stressed.
2. After long term use it messes with the brain causing you to loose minor brain cells and become more iritable.
3. The resedue from taking it (smoke) is terrible for your lungs and can cause lung cancer and makes you cough up tar.