The video games -> violence argument is hard to make, because it involves trying to find a causal relationship in the data. Identifying addictions, though, is fairly straightforward. It doesn't surprise me at all that kids are struggling with addiction to electronics. Our brains probably aren't built to handle so much instant gratification.
Instant gratification makes sense. It makes me wonder if that's why easier "casual" (I loathe the term, but still) games are more popular with younger kids while older kids and adults tend to go for more difficult games.