Haven’t read any studies, Where Angels Fear, just my observations. Some of the children I observed I know well enough to say several of them are well-adjusted, to the best of my knowledge, and were very adept at playing their video games.
As for my own grandson, he was good at the superhero game he had, progressing through many levels of the game very quickly. An adult family friend who is a gamer played with him and was impressed with his skills so I assume my grandson was not unskilled at the game nor was he incapable of improving.
Before getting the game, he was social, argued less with his sister, did not hang out in his room. Those behaviors began while he was playing the game and disappeared when he lost interest in it. He still plays that and a couple of other games but very infrequently and prefers to be outdoors playing soccer.
I would not suggest that these games make people violent. I think the root of violence is much deeper than that. However, I firmly believe regular use of violent games can lead to anti-social behavior and to a desensitizing to pain, suffering, and violence of all sorts. Again, my opinion and observations. But, I will add that our adult friend who is a gamer, and does participate in violent games, says that when she was younger, she noticed a desensitization in herself and quit playing for several months, gradually participating again but being conscious of her feelings during and after games. She said as she aged, the effect lessened. Which leads to me to wonder if the most negative effects are on adolescents whose personalities are not fully developed?