Utter bullshit.
I have known cokeheads, heroin addicts (my ex, sadly, got into it when she was with her next boyfriend and guess who was there to help pick up the pieces,) crack addicts and I've personally had many a point in my life where I've abused weed (yeah, I do think there's such a thing as using it TOO much, and as much as weed isn't anywhere near the hard stuff, having a psychological dependency on it can be crippling.)
I have known hardcore games, have been one myself, and have been prone to 24 hour gaming sessions myself.
Totally different things, totally different situations, totally different effects.
Long gaming sessions are a not only just common, but they are an accepted part of our culture and our hobby.
I'm sure we've all had parties where we've stayed up all night getting drunk and playing guitar hero with some friends until dawn (and those of you that haven't, you're welcome round to mine so you can share the good vibes \o/.) I'm sure most WoW players have pulled many an all nighter for the sake of getting that piece of gear they so desire, and I've taken to staying up all night doing menial jobs for backstabbing, two-faced, time wasting assholes in Red Dead Redemption lately.
Long gaming sessions are THE NORM in this culture, drug habits, psychological and physical dependency are NOT.
Yes, there are people who take it too far, yes there are people who do become addicted to games, but I think the only reason that Doctors believe that because a kid's staying inside choosing to play a video game over going out for a bike ride or something is because there is still a heavy bias against gaming as a culturally accepted medium.
There is STILL a stigma that games are just kid's toys, there is still a stigma that games are a waste of time and that a piece of gear in an RPG is actually worthless (when it infact isn't, because whether real or fictional humanity becomes attached to people, places and objects.) Nobody has a go at the bookworms for buying their faces in Pride and Prejudice for the umpteenth time rather than socialising and nobody complains when movie buffs watch all 3 Lord of the Rings or Godfather movies back to back.
GAMING IS NO DIFFERENT.
Fuck these Doctors, seriously. They get their PhD. and then believe they understand how everybody's head works while forgetting the one most crucial element: CONTEXT.
Not everybody is a social butterfly, nor does anyone want to be. I'm quite the introvert myself but I feel perfectly psychologically healthy. I refuse to be labelled an addict because I prefer to spend my time listening to music, watching movies or playing games.