This article, published by the American Academy of Child and Adolescent Psychiatry, talks about how TV violence can make children be more violent themselves. It states that television violence can make children immune to violence, help them accept it as a form of problem solving, and cause them to imitate the violence that they see on TV.
In discussion sections, we have also gone over these same findings, and have generally concluded them to be true. However, we were also given articles to read that maintained that violent television and games had positive attributes as well; one even claimed that this violence helps to decrease violent behaviors in adolescents.
Overall, I feel like this is an issue where the correlation doesn't equal causation principal applies well. We are not sure whether aggressive children, are more likely to watch violent shows, and therefore are simply more violent because they already had the tendency to be more aggressive. It could also be that children who grow up in more violent environments have parents who do not care what they watch, so they are able to watch more violent television. These children may grow up to be more violent, even though the television they watched may not be to blame.
Therefore, before judgments are made, more controlled experiments are needed to determine the cause effect relationship. That can be seen in the video we watched in class, because they compared children's reactions to Barney and the Power Rangers. The video showed that the two shows brought about completely opposite behaviors, suggesting that the Power Rangers did in fact invoke violent behaviors.
In the end, however, we cannot conclude from these studies if these behaviors correlate into long term effects on the children or not. So, more information is definitely needed to report the cause effect relationship to be confirmed.