American teenagers are sharing more information about themselves on social media sites, but taking steps to protect their privacy online, a study showed Tuesday.

The new survey showed 91 percent of those surveyed posted a photo of themselves, up from 79 percent in 2006; 71 percent post the city or town where they live; and 53 percent posted their email address.

But the survey of youth aged 12 to 17 also found 60 percent of Facebook users set their profiles to "private," which limits who can view their data.

And 56 percent said it was "not difficult at all" to manage the privacy controls on their Facebook profile, according to the survey by the Pew Internet & American Life Project in collaboration with Harvard's Berkman Center.

A relatively small percentage expressed concern about third-party access to their data: just nine percent were "very concerned."

The researchers said focus group discussions with teens showed "waning enthusiasm for Facebook."

"They dislike the increasing number of adults on the site, get annoyed when their Facebook friends share inane details, and are drained by the 'drama' that they described as happening frequently on the site," the report said.

"The stress of needing to manage their reputation on Facebook also contributes to the lack of enthusiasm. Nevertheless, the site is still where a large amount of socializing takes place, and teens feel they need to stay on Facebook in order to not miss out."

At the same time, teens are becoming more interested in Twitter: the study found 24 percent of online teens use Twitter, up from 16 percent in 2011.

The typical teen Facebook user has 300 friends, compared with 79 followers for those using Twitter.

Girls and older teens tend to have substantially larger Facebook friend networks compared with boys and younger teens, it found.