I could have qualified as one of that 9 percent when I was younger.
Maybe still now, I have a good few hundred games on PC, PS3, PS2, XBOX360, PS1, SNES, PSP, gameboy...
Yes I spend more time gaming than someone who doesn't game (for lack of a better verb).
20 hours per week? Not now, but when a new game I was looking forward to comes out, yes I would exceed that if I liked the game.
But do I deprive my body of food so I can spend more money on games?
Do I miss out on sleep so I can keep playing till 6AM?
Does playing games affect the state of my mind in a detrimental way?
No to all of these.
Yet if the definition of gaming addiction was limited to how much I was into it, I would probably qualify.
The idea of gaming addiction is too sensationalist right now for anything someone has to say on the matter to be unaffected by that stigma, but it's not a myth, it does happen - it's just alot rarer than this study makes out.
However I think most would agree it is a symptom in itself, not a disease. Gaming does not *cause* gaming addiction (most of the time... Eve Online or Minecraft or WOW could be called addictive and I wouldn't argue).
Being addicted to something like playing games IMHO is a symptom of some other problem (or just an aspect) of that person's personality. It also helps that they are immensely fun!
People choose to do things in life more often than not because they are enjoyable in some way, that's pretty much what it boils down to.
Gaming is a hobby for most, but as with any hobby some take it further than most of us would.