You need to take a step back and think about this.
Alright first let me say that my views are just my own, and may be somewhat biased as i do partake in the occasional substance abuse sessions.
I see what your trying to say, Drugs are Bad. Everyone knows that drugs fuck shit up, However- i dont agree with the way you have gone about trying to get your message across. Im trying not to get into a debate over the evils of drugs here.
Essentialy put, you are preaching to the converted. The only people who will take this seriously are those who already agree that weed is a dangerous drug while almost everyone who is into it is just going to laugh at this, because thats what it is; Hilarious Bullshit.
People who do drugs already know that they are fun, social devices (Which is the whole reason why they do it!) Unfortunately for you, Weed is such a terribly minor and impotent drug and because of this there is very little evidence against it, mind you it has been proven to change your mindset subtly and this can be bad for kids who are coming up for exams in school and there is the threat of psychosis (Which is probably what you should be using to scare people into not using because there are those few people who do have their minds fucked by the drug, simply because its the way that that persons brain is).
Like many others have said, the imagery you used would be much more suited to alcohol, because Alcohol kills infinately more people than weed every year and yet its legal and easily available.
If you are going to make an anti drug statement, make it about the drugs that do fuck shit up like Alcohol, Nicotine and Opiates.
People need to get their priorities in order.