Growing up my parents had a strict rule of only 1 hour per day playing xbox/playstation/whatever video games. Now if a kid is playing video games for only an hour a day, they're barely playing any at all. Looking back, it definitely effected my life in negative ways I did not realize then. I imagine 4+ hours or anything like that per day gaming has a huge effect (some positive, but mostly negative) on the development of 6-17 year old kids.
If anyone has a good research article on that issue I would be interested in reading it as my thoughts are only speculation.