Using Facebook and other social networks can have some significant negative effects on teenagers and young adults, says a California State University researcher.

Actually, using sites like Facebook can be linked to some serious psychological disorders, like narcissism for teenagers and antisocial behaviors, mania and aggressive tendencies with young adults, says Dr. Larry Rosen, professor of psychology at California State University.

Rosen presented his findings, which he pointed out are new and not yet ready for publication, at an American Psychological Association conference. He noted in his presentation that teenagers and young adults are highly attached to their digital devices, spending a lot of time on social networking sites and often communicating with friends and relatives by text message instead of over the phone or face-to-face.

Rosen pointed out that 42% of teenagers say they can text blindfolded.

And he's far from alone in talking about how much time people are spending on social sites and using devices. Last summer, a survey showed that 57% of the women polled said they communicate with people more online than they do face to face, and 39% called themselves Facebook addicts.

That study echoed survey by gadget seller Retrevo which claimed that people are often obsessed with social networking sites, noting that 48% of those polled said they update their Facebook or Twitter accounts during the night or as soon as they wake up. It also found that 19% of people under the age of 25 post Facebook or Twitter updates anytime they wake up during the night.

Rosen said overdoing it on social networking sites can draw out negative emotional behaviours. However, he was quick to point out that he's not trying to imply that Facebook creates psychological disorders. That has not been shown.

"We feel that either one of two mechanisms is at work here," Rosen said. "If you already have narcissistic tendencies, these 'behind the screen' media will bring them out since you are not talking directly to people, only a screen. However, for the same reason it also encourages you to display those same signs and symptoms through your writing/posting/photos."

Dan Olds, an analyst with The Gabriel Consulting Group, said he's not surprised to hear these kind of results.

"New technology always gives users new ways to indulge both their best and worst traits," Olds added. "Just as the telephone made it easier to reach out and touch someone, it also made it easier to reach out and annoy someone or act creepy. Social networking isn't any different."

Facebook has not yet responded to a request for comment.