yeah i think it can mess up your head....especially if you are young.
i thought i fucked my head up...but i cut down and just realised that i was smoking too much for my head to cope with.
If you think its fucking your head up stop smoking or at least cut down....cause no-one can really tell you how fucked your head is...its just a matter of dealing with how fucked your head is.

I also smoked through my gcse's and failed 2 i re-took one this year while possibly smoking more than i was before and passed it.
It really depends what you mean by fucked....

And dontsmokethe roach...you know your avator thing....its weird how he does the kickflip with his back foot...unlees he's skating towards the screen.