I'm going to agree with you OP to an extent, but I believe gaming becomes the outlet rather than the cause of these problems. 30-40 years ago we never had the "escapes" that we do now, so people who maybe had low self-esteem or were slower developing socially over their teenage years just had to suck it up and deal with it. Now on the other hand, when we start to lag behind, we find our outlets in games, or the internet, where we don't have to come into contact with people, no one cares what we look like, where we can have some sense of achievement.
It's a quick fix essentially. At 18 years old the thought of never having a girlfriend might weigh heavily on the mind of a normal person. Feeling helpless and abnormal, we stick in a game, try and get a higher gamerscore or maybe go online and come top in a few games of (insert fps here). This makes us feel good for a small amount of time. The underlying problem is still there however, that we feel abnormal and apart from our peers. That then grows into anger and disdain for the rest of our age group. We hate the "normal" lifestyle because as much as we protest otherwise, deep down we wish we were a part of it, we just don't know how to be.
It's possible it affects those people more who started gaming at a young age. My brother and I had a megadrive when I was around 6. Partially due to over protective parents, partially due to being a little overweight and not wanting to face the bullies, we didn't "go out and play" as much as the other kids, instead we'd sit playing Sonic or Golden Axe. It was comfortable, it brought us enjoyment, it became an escape.
Things didn't go too badly after that untill I hit 13, at which point I went to an all boys school. Before leaving middle school I had just started to become interested in girls, had just started to learn how to speak to them. Having no real social life outside school I quickly got left behind as others used their highschool years to figure the whole boy/girl thing out. I wasn't alone though, in my school a group of around 20 kids were all in the same situation and we quickly became the outcasts or social Pariahs of the school. Gaming again became the release, untill it became the thing I enjoyed most. When I eventually did start going out at 17, I had no idea how to interact, especially with the opposite gender. I dived quickly into alcohol and smoking, again quick fixes to help curb the underlying problem that I am socially inept.
As for now, at 22...well it's a Saturday and instead of heading off into town to try and pull, or going out otherwise with my friends, I'm sat here typing this out, so what does that tell you?
Gaming itself doesn't have a bad effect on our mental health, but combined with other factors it can seriously stunt your development in other areas. This then leads to anger, being miserable and gaming or spending time on the internet more to make up for it.
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