One researcher found no increase in aggression when payers shifted between non-aggressive, moderately aggressive and highly aggressive video games.(1)
There's no clear causal relationship between game playing and school performance. The detrimental effects of games isn't clear and contradictory (2)
One study found no relationship between heavy video game playing and psychopathology or social introversion. (3)
Another study found no significant relationship between generally aggressive behavior and video game use (4)