Well actually that sounds decent. I have a theory that goes like this...

It is very likely that during the paleolithic era and perhaps before...that man used to starve themselves as a way of dealing with depression or bad emotion (like how emo people cut themselves)...and it is likely that God created marijuana to help heal the mental pain and also is used as a way to communicate with man telling him/her to eat and to feel better. its as if God wants to make our existance as good as possible on this earth that he has created for us. And if you think about it....only society and humans are the cause of depression.