The thread title is a lie!
Weed doesn't effect brain development in any significant way, unless you smoke yourself sick. Case in point: I have many friends that smoke weed. One is the smartest little dickwads you'll ever meet, the kid has a 4.0 and can figure out problems before you even finish reading them. He will finish his masters this year, I am really proud of him, and he lights up multiple times a day. I also have another friend, who god help him, he is the dumbest little wigger gangsta wannabe you could ever meet in Atlanta. I'm sure if he's awake, he's high right now.
People who are dumb who smoke, will always be dumb, and smart people will remain smart. Although I don't smoke, I do think it should be legalized and monitored, like alcohol. I mean, c'mon, the shit is easier on your system than cigarettes, jesus...