Does Marijuana cause some sort of brain alteration?

I've read all the arguments and I know all the short term effects... I'm not talking about long term use, just like 5 times or something, so forget those effects. I'm talking about once the marijuana enters your system for the first time, does it alter your brain at all? Especially in teenage years? I know that there are many successful people who supposedly smoke, but all of the people I know who have smoked aren't exactly the brightest, smartest, or overall most pleasant people that I know. Help me out here, and try to use facts.