Mary Ellen Handy, now a junior in a private high school for girls in northern New Jersey, has a message for anyone who thinks cyberbullying isn't so bad. Not only was her freshman year of high school absolute hell emotionally, but she developed ulcers and other physical ailments from her experience.

Things got so bad that Handy couldn't keep food down and would lie on her couch at home, holding her stomach and crying for long periods. Mary Lou Handy, Mary Ellen's mother, says her daughter is usually unflappable and, with two older brothers, is accustomed to teasing around the house. But this was different, and Mary Lou--a middle-school teacher who has seen her share of schoolyard fights--says she was surprised at "what that type of stress can do to someone physically."

Mary Ellen is just one example of a paradox of online life: Kids use the Internet to connect to other people, with E-mail, instant messaging, blogs, and social networking services like MySpace.com. But the Internet also can be a place where kids are harassed or become so engrossed that they're practically swallowed by their computers.

Some kids who run into these problems become isolated and depressed, their grades suffer, they develop eating disorders, and they fail to develop real-world social skills. And online role-playing can turn kids into habitual liars.

One 16-year-old boy who was dumped by his first serious girlfriend over the phone found a fuller explanation for her actions on her instant messenger profile. Their entire network of social contacts--friends of friends in multiple high schools and so on--also learned that the breakup was about a lack of "chemistry" between them. The boy skipped school the next day, and he wondered aloud to his stepmother why the information had to be on the Internet for all to see.

Parry Aftab, a privacy lawyer who founded Teenangels, an organization that teaches kids about online safety, says the breadth and depth of new types of behavior among children related to Internet use has made her rethink Teenangels' mission. Its focus is now what she calls "cyber-wellness" instead of just safety. Parents can take action to mitigate some of the negative effects on their kids (see "How To Protect Your Kids", below).

How To Protect Your Kids TALK TO YOUR CHILDREN. Let them know they can come to you if they're uncomfortable about anything they experience online, without fear of being scolded. KEEP THE FAMILY PC IN THE OPEN, such as in the living room. Children are less likely to sneak into a dark corner of the Web if they know a parent may suddenly look over their shoulder. WATCH FOR WARNING SIGNS of problems: falling grades, skipping school, personality changes, reluctance to leave the PC, decreased time with friends. SET RULES and talk about your expectations. Change the rules as the child matures. HELP INITIATE REAL-WORLD ACTIVITIES for your child, through school and religious organizations or sports teams. If your child's life is good overall, chances are he or she is less likely to get into trouble online. GO ONLINE TOGETHER with your child. Check out baseball scores, learn about constellations--then go out and see the real thing. Share interests and have fun.

Dr. Robert Kraut, a professor at Carnegie Mellon University who has studied online behavior for more than 10 years, says that happy people use technology to support their in-person relationships instead of using it to make new friends online. "Lots of people are figuring out where E-communication is fitting into their lives and, in many cases, are doing it successfully," he says.

Of course, nobody can know for sure what the future will bring for this most-wired generation of 12- to 18-year-olds. It may be pointless to think too far ahead, because technology changes too quickly for anyone to measure its effects with certainty. Parents have always worried about the spread of new technology--including television in the 1960s--and most people ultimately adapt innovations into their lifestyle in a healthy way, or at least in a way that does no long-term harm.

Still, the Internet and technology are so pervasive in the lives of children and teens that one can't help but wonder how harmful they might be. Some 82% of kids are online by the seventh grade, according to the Pew Internet and American Life Project. And a Kaiser Family Foundation study last year found that people from ages 8 to 18 spend an average of 6.5 hours each day connected to something electronic. If you count the time spent multitasking--updating a MySpace Web page while listening to an iPod, for instance--that number jumps to 8.5 hours of online activity packed into 6.5 actual hours.