The nationwide hysteria over Justin Bieber...or "Bieber Fever," as some people refer to it...can easily become an obsession among teen girls.  Maybe even an UNHEALTHY obsession.

One "expert" claims it could actually be HARMFUL to a kid's mental health.

Dr. Alan Ravitz, a child psychiatrist, says that even though young girls have been freaking out over teen idols for decades . . . things are different now, because of stuff like Twitter and Facebook, which allow fans to feel intimately close to the stars.

For one, Ravitz is concerned about the "death treats" that Justin's "fans" sent SELENA GOMEZ, when pictures of them kissing popped up online.

He says, quote, "Where are the parents?  Who's trying to guide these kids?

"Who's telling them to be polite and civil to each other?  In a way, it's analogous to terrorism, where the only thing important is your own personal agenda and if anyone gets in the way of that, you're allowed to do whatever you want to them."

He adds, quote, "If you're a 10-year-old and you get a Tweet from Justin . . . you can't think, 'Well, he probably has a PR person who generates these tweets for him.'  You as a 10-year-old think, 'Oh, he's sending this to me, he is telling me about his life.'

"So on the one hand, he has this PR team creating this sense of false intimacy, and on the other hand he creates a problem for himself because he encourages intrusion into his private life.  I don't think he can have it both ways."

But while Ravitz seems to be saying that Justin's people are complicit in all this . . . he does believe that ultimately parents have to keep their kids grounded.

He says, quote, "I think it's the responsibility of the fan base to get realistic about their perceptions.  It's less Justin Bieber's responsibility, and more the responsibility of the parents of those kids who reacted so uncouthly.

"[Justin's management is] just focused on revenue generation, which is a reasonable thing to be focused on . . . running a business."

So if these girls are susceptible to becoming TOO wrapped up in Justin's world . . . 2.0, or otherwise . . . what exactly are they in danger of?  Well, that's a little unclear.

Ravitz says that kids with pre-existing psychological issues are more likely to be negatively affected by becoming overly obsessed and preoccupied with Justin Bieber.

But Ravitz says that he doesn't see things getting TOO crazy.  He adds, quote, "I don't think anyone's going to kill themselves if Justin Bieber has his hand on Selena Gomez's butt."

(If you have a young girl, or boy, who follows Justin on Twitter, what do you think?  Do you think it's harmless . . . or do you think it can allow kids to feel TOO involved with a celebrity?)

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