Me & a friend separately had different versions of the effects of over-gaming
I got really into Need for Speed: High Stakes while at Uni and, while driving IRL, I caught myself subconsciously reaching for the handbrake as approached a sharp 90 degree bend. In a 1.0 Micra full of students.
My friend's version of this happened after playing Half Life 2 all night and going to work with no sleep; he started hallucinating some of the enemy NPCs on his screen and kept trying to shoot them with the mouse. Afterwards he had absolutely no idea what he'd actually clicked on while doing data entry for a bank.