(I wasn't able to reply directly to the comment above).

There was no "become" gaming addicts in this study, the study looked at brains of addicts vs. non-addicts (not before and after). It is likely that brains of addicts are different than non-addicts to begin with, but this study is simply acknowledges that there are gray matter differences that might explain the pathenogenesis of the addiction; ie what perpetuates it, and how might these changes explain what symptoms and psychiatric symptoms we see in gaming addiction.

In gaming and internet addiction research in general, the chicken and egg question is a legitimate one, but research suggests there are bidirectional influences that create a vicious cycle. In other words, vulnerable brains are more vulnerable to screen addiction, and then the addiction contributes to psychiatric pathology, which worsens the addiction, etc etc.

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