The most commonly accepted theory is different video games have different effects on different people... In other words, it all depends
I can't deny, what SpideR said about addiction is true, I am well and truly addicted, because of PC's etc and TV's screens, my eyes are completely f@#!ed, plus working nightshift, whenever I go out in the sun I squint my eyes sooooo much, I can never keep my head up lookin straight, unless it's dark/dull outside I always have to look down it sucks... I'll never be able to drive because I don't trust my eyes...