Some kids play games... others are obsessed with them.

These kids practically live in their virtual worlds--and new studies show that when it goes too far, it can lead to some very real-world problems.

In the first study, researchers surveyed 3,034 children in Singapore from third grade through eighth grade every year from 2007 through 2009, and found that while nearly all of them played games, about 9 percent went much further.

They were addicts.

And the researchers wrote in Pediatrics that these hardcore gamers--many of whom spent more than 30 hours a week lost in the digital rabbit hole--were less likely to fit in with their peers and more likely to suffer from anxiety, depression, anxiousness and impulsive behavior.

And, needless to say, they didn't do very well in school either.

But it's not all bad news--because the researchers also found that when these addicts had their games taken away, the problems practically vanished.

Of course, not every kid is hooked on games. Others are caught in the Web--the World Wide Web, and another new study finds that young Internet junkies risk depression, sleeplessness and even obesity.

Swiss researchers surveyed 7,200 teens and young adults between 16 and 20 years old, and found that those who spent more than two hours a day online were more likely to be depressed.

Girls were more likely to suffer: The researchers say young ladies who spent the most time plugged in were 86 percent more likely to suffer from depression, while young men were a third more likely, than those who spent less time online.

The researchers also found that the young men who were the heaviest Internet users were more likely to be heavy elsewhere: They had a higher risk of obesity.

And the gals were more likely to miss out on sleep as a result of their Internet activity.

Put it all together, and that means it's time to set limits on your children and grandchildren when it comes to games, Internet and even the television and cellphones.

Just don't be too strict about it--because the study also found that kids who spent too little time online were also more likely to be depressed.

After all, most kids who play videogames and use the Internet manage to do so without putting their lives on the line. These activities can be fun and even educational, as long as they don't cross the line into overuse and addition.

The trick is knowing when it crosses that line--but if you're a parent or grandparent, you can usually tell.