Nowhere in the bible does it say that smoking marijuana is a sin. I guess aslong as it is not an idol to you then it is fine from a biblical perspective . In my country marijuana is legal now ,but before it wasn't I guess it is probably wrong to break the law but as long as you are not cultivating or dealing it then you aren't brealing the law. If marijuana does come before your relantionship with God then there is no reason tonbe against it. Marijuana has many psotive effects on one's mental state in my opinion. For example marijuana makes you the opposite of aggresive and also makes you more sensitive towards the feelings of others. The bible does say that it is not what you put into your body that makes it good or bad but rather what comes out. Alchol for example can make people do terrible things like commit domestic violence and for that reason the Bible is against getting drunk but not opposed to drinking.