The relationship between playing video games and violent behaviour isn’t as black and white as most people assume. There is neither the causal evidence that would support the tabloid alarmist headlines that blame Mass Effect, Call of Duty or World of Warcraft for mass shootings nor the evidence that video games are entirely benign.

We know from research that trauma has a significant and lasting impact on the brain, a pattern widely accepted across numerous studies. For those who have already been traumatised and/or have maladaptive social skills, that increase in arousal sensitises the brain to further threat. It also makes them more likely to respond with anger or fear to a neutral stimulus, perceiving it as a threat. We also know from research that when the threat sensor in the the brain is activated (the amygdala and limbic system) the prefrontal cortex pretty much goes off-line until the threat is resolved. That significantly reduces the person’s capacity for empathy, complex reasoning, social skills and ability to be aware of the impact of your own behaviour on others. This effect is amplified where there is an absence of healthy real life relationships and/or physical exercise (which produce oxytocin, and help to mediate cortisol and adrenaline). And of course we know that people who have raised arousal levels deliberately seek out experiences that match or use that level of arousal, so they are often much more interested in violence and gore than their peers.

That’s all well established neuroscience. We also know that these brain changes can be perpetuated by exposure to violence or the representations of violence in our daily lives or the media we consume. Exposure to violence is an unseen public health epidemic. We also know that this pattern of being over-sensitised to threat and in a heightened state of physiological arousal gets ‘stuck’ for a proportion of maltreated children, particularly where there is an absence of secure attachment figures, and that ‘acting out’ with violence in this group is much more common. The neurological basis for moral reasoning and antisocial behaviour implicate similar brain regions. Similar areas are also implicated in violent behaviour when this is related to a lesion, dementia or atrophy.

Having reviewed the evidence, I think it is clear that video games do not in themselves cause violence. But playing violent video games increases physiological arousal levels (readiness for fight or flight) just as we know is the case for exposure to real life conflict such as domestic violence within the family. This can create a lasting effect which shows in MRI scans. But the effect is quite specific. We know that MRI studies show differences in the brain when people play violent video games but not when the video games do not involve aggression. We also know that it is dependent on the social acceptability of the behaviours chosen in the game.

It seems likely that watching films or TV can similarly cause an increase in physiological arousal, but this would only be the case with a high level of violence/action/drama, something which is not normally sustained for hours upon end the way it can be in some video games. Also, video games are more immersive because they are interactive, and I suspect you don’t become as habituated to them because of the fact that there is variation on every presentation of the stimulus, whereas rewatching the same film gets dull and predictable and no longer gives us that visceral response. Thus I think that it is reasonable to consider violent video games as a particularly concentrated form of this stimulus.

It seems from the meta-analysis that a small scale shift towards higher readiness for fight or flight and lower empathy/insight/reasoning is happening all over the place amongst people who play a large volume of violent video games with the result of small but measureable increases in the risk of aggressive behaviour. I’d extrapolate from this to what is currently happening with the threats and harrassments towards women and minorities in the gaming space, to suggest that this combination of lack of nurture and exposure to violent material may be contributing to the lack of empathy and insight into the impact of their behaviour amongst people involved. But I suspect that the impact of video game play on real life aggressive behaviour is only a significant issue at the individual level where this is combined with the presence of trauma and/or the absence of nurture. After all, the move from enacting violence in a video game to doing so over social media is much smaller than the move to take actions outside of home technology where you can see the impact on the recipient.

It is only in the extreme examples, where you combine violent video game use with people with horrendous histories, a lack of secure attachment relationships and/or who have entrenched extreme views (eg about women), nothing else in their lives to constrain them, an echo-chamber of harmful views including incitement to violence, and perhaps mental health problems on top that the mixture becomes truly toxic. Amongst this group a small proportion take the threat-talk that is so prolific online and in video game spaces into horrific real life actions.

I can’t see that being so different to the proposed mechanism for lots of other phenomena. As with the relationship between cannabis use and psychosis, or alcohol consumption and suicide, the former is something most people consume without harm so it cannot be causal in isolation, but for a much smaller number of  people with increased vulnerability (genetic, epigenetic or experiential) it can be a contributory factor towards a more negative outcome.