In my experience, the parents who allow their children to play violent video games are often the ones who don't seem to care about their child's antisocial behaviour towards others anyway. This seems to suggest that in many cases, not all, the fault lies not with the game but with parental values. While there is definitely a correlation, the saying goes that correlation doesn't always indicate causation. Children who have a tendency towards violence are more likely to be drawn towards aggressive games. Game developers are therefore doing as all facets of the entertainment industry do; appeal to a target audience. Not create a target audience.
The only negative effects is eye damage, and its your own dumb ass fault for sitting so close to the screen, so how about you remove this nonsense thread (I've studied the effects of gaming myself and they never say the positive side effects)