How have pornographic materials included in games such as GTA and Tomb
Raiders Lara Croft (as a sexy figure) affect teens with their social
relations? Are children affected socially by playing such games as
it?s an easier route of virtually experiencing relations? I.e. picking
up prostitutes in a car (GTA). Does including half nude female figures
in fighting games affect teens in any mental way?

http://playstation.about.com/b/a/188332.htm

Our local paper, the Columbus [Ohio] Dispatch had a front page article
on gaming today (July 5th).  It speaks of an addiction similar to
crack and mentions the world's first detox clinic for video-game
addicts opening this month in Amsterdam.  Might get you started on
some research.