I think it depends on how you use it. It is illegal for one, which automatically is enough of a reason to not do it. We are to obey the law. However, in the case of medical marijuana, I also think it can be helpful. God also made fire, carnivorous animals, and other harmful things... but they also serve their purpose. I do believe that there is a reason God made weed, but I don't think it's necessarily right for humans to smoke it. There is a verse in Isaiah however that refers to smoking for meditative purposes and I have yet to study that out. I was just talking about it the other day with some people. In my opinion, it should be legalized for many many reasons that I'm not going to go into in this post. But to answer you, yes, God made it. Is it a sin? It can be, and it could have good uses as well. So, one thumbs up and one thumbs in the middle?