Nope, I'm not trolling. I seriously believe that video games cause violence and I'm going try to convince you of the same. Hear me out on this one; I'm not going to use the same arguments used by crackpot soccer moms and alarmists in the media. However, this may clarify (to a certain extent) why there are so many reports about the effects of violent media that conflict one another.
Now then, time for the kicker: Violence in media does not cause violence. Video games still do. It doesn't matter if you spend your days playing God of War or Kirby, relying on a solo activity to fill your spare time in lieu of social interaction will cause psychological problems, which can further result in violence. http://www.escapistmagazine.com/articles/view/columns/ask-dr-mark/10177-Issues-Gamers-Should-Think-About Even the Escapist's Dr. Mark touches on how video games can damage social skills over time in the previous link.
As we as a modern society depend increasingly on electronic media of all kinds to make connections with people without actual face-to-face contact, and therefore we sacrifice the social skills we could have developed by going out and learning how to hold an actual conversation. People settle for less because they are afraid of being judged or do not know what to do around other people. They bottle themselves up and eventually explode. It's not the actual content of the games that causes violence, it's playing games non-stop just to get through the day.
The reason why video games are becoming such a huge problem now is a huge shift in the demands of consumer markets, primarily brought on by radical changes in game design over the last 7 years or so. technology has advanced to the point that games built with 70+ hours of solo playtime is the norm. Look at Dishonored. It was a massive success, but it's main flaw in the eyes of consumers was its short lifespan and lack of replay value. Any gamer in high school can save up $60 to buy the new Assassin's Creed. They can come home from school and play it for all it's worth all day every day. When they're done, it's just in time for the new Elder Scrolls or CoD or what have you. Basically, the stream of input can theoretically never end. With it, extra-curricular socialization can completely vanish.
Multiplayer has taken an even darker turn for the worse. Back in the olden days, it you wanted to curb-stomp your friend in Halo, you had to invite him over to your house and proceed to empty hot lead into him. Nowadays, if you want to grab your buddies for a game, you talk to them through a screen. With only your voice. There's no form of self-expression past whatever can be conveyed through a mic and whatever customization options that particular game allows.
I'm going to summarize this briefly: Stop playing so many video games. Learn how to make small talk. I don't care how. Use some kind of online guide if you feel minimalist. If that fails (which, in reality, is totally possible) go see a psychologist or attend a social outing where groups of people meet each other all at once. Keep gaming in moderation. I very much appreciate it if you read this entire post. Thank you.