One out of every seven Los Angeles high schoolers with a cell phone has sent a sexually explicit text message or photo, according to a 2011 survey that also found "sexters" more likely to engage in risky sex behaviors.
"No one's actually going to get a sexually transmitted disease because they're sexting," said Eric Rice, a social network researcher from the University of Southern California in Los Angeles, who led the new study.
"What we really wanted to know is, is there a link between sexting and taking risks with your body? And the answer is a pretty resounding ‘yes,' " he told Reuters Health.
A study of Houston high schoolers out earlier this summer found one in four teens had sent a naked photo of themselves through text message or email, and those kids were also much more likely to be having risky sex.
Rice's findings, published Monday in the journal Pediatrics, are based on 1,839 students in Los Angeles high schools, most of whom were Latino. Three-quarters of them owned a cell phone that they used regularly.
On a survey sponsored by the Centers for Disease Control and Prevention, just over 40 percent of teens with a cell phone said they'd had sex, and about two-thirds used a condom the last time they did.
Rice said the rate of teen sexting in Houston may have been slightly higher than in Los Angeles because of demographic differences - but that overall the two reports are consistent.
"Somewhere in the middle is probably a pretty good estimate of what's going on nationally," said Jeff Temple, a psychologist and women's health researcher from The University of Texas Medical Branch in Galveston who worked on the Houston study.
His research found that girls in particular who'd sent naked photos were more likely to engage in risky sex, to have had multiple recent sex partners or to use alcohol and drugs before sex.
"Sexting appears to be a reflection or an indication of actual sexual behavior," Temple told Reuters Health.
"What they're doing in their offline lives is what they're doing in their online lives."
Rice agreed that was the most important finding to take away from both studies. "That may be a no-brainer to some parents, but it may be alarming to others," he said.
"This is a behavior that a minority of adolescents are engaging in, but that minority is engaging in a group of risky sexual behaviors… not just sexting."
With sexting, there's also the concern that naked photos will end up on the Internet and teens will be bullied online, or that students who receive explicit texts could be charged with child pornography.
Researchers still have a lot of questions about sexting, including which students are most likely to sext and what other behaviors or personality traits may be more common among sexters. Temple and his colleagues are currently working on a study to see what typically comes first among teens - sexting or sex.
For now, Rice said parents and teachers may be able to use media coverage of the latest celebrity or politician sexting controversy as a way to talk to teens about sexting and actual sex – especially because the two are so closely linked.
"Sexting might be an easier conversation for teachers to start having with teens than a full-on conversation that starts, ‘Let's talk about sex,'" he said.