This one is tricky—namely because it has a lot to do with the type of game your kid is playing and the type of kid you’re dealing with. The NIH-sponsored study mentioned above found no statistically significant link between gaming and aggression; however, kids who have aggressive temperaments might find those proclivities rewarded and reinforced by violent games, by the same mechanism (i.e., the brain’s reward system and all that dopamine) responsible for reinforcing addictive behavior. Indeed, the folks at Brain & Life report that just 10 to 20 minutes of violent gameplay can cause an increase in aggressive thoughts—and the reward system is one part of the problem.
What’s more, numerous psychological studies have concluded that violent video games, in particular, trigger the brain’s fight-or-flight response—a state of hyperarousal that, when occupied too often, can lead to chronic stress. According to a 2016 article published in Psychology Today, “once chronic stress sets in, blood flow is directed away from the higher thinking part of the brain (the frontal lobe) and toward the more primitive, deeper areas necessary for survival, causing impairment in functioning.” At the very least, this fight-or-flight response is short-circuiting the brain and all but nullifying the frontal lobe benefits that kids can reap from wholesome, moderate gameplay; when it becomes a chronic issue, anxiety, emotional dysregulation and behavioral problems, including aggression, might follow.