More than one in five "at-risk" middle-school aged children have recently engaged in "sexting," a practice where one sends sexually explicit messages and/or pictures by cellphone, according to a new study Reuters reported.

Researchers found that adolescents with behavioral and emotional problems that sexted were more likely to engage in some type of sexual behavior, compared to adolescents who said they didn't sext.

"We know early adolescents are using mobile phones and all forms of technology more and more and we know that early adolescence is a time when people become engaged in sexual activity," Christopher Houck, the study's lead author, told Reuters. "So how those two connect is an important area of study."

For the study, researchers recruited 420 middle-school aged children from five urban public middle schools in Rhode Island between 2009 and 2012. The students were given a questionnaire regarding risky behaviors and behavioral and emotional problems.

Based on the questionnaire, 17 percent of the participants said they have sent a sexually explicit text messaged in the past six months, while 5 percent reported sending sexual photos by cellphone during the same time period.

"Sexting behavior was not uncommon among middle school youth and co-occurred with sexual behavior. These data suggest that phone behaviors, even flirtatious messages, may be an indicator of risk. Clinicians, parents and health programs should discuss sexting with early adolescents," the study authors wrote.

Researchers found that teens who sexted also were more likely to report intentions to engage in sexual activity. They were also more likely to feel that their peers, family and the media approved of this behavior, HealthDay reported.

Adolescents who said they were further along in puberty and those who had trouble processing their emotions were most likely to report sexting. The study also indicated that children who sexted struggled more with emotional competence, and they had less emotional awareness than their peers.

"It could be that for kids who have trouble with emotional processing that it's a little bit easier to sext somebody than to say face-to-face, 'Hey, I like you' and see what that response is," Houck, a staff psychologist at Rhode Island Hospital's Bradley Hasbro children's Research Center in Providence, said.

Teens who sexted were twice as likely to touch genitals over clothing, 2.7 times more likely to have oral sex and 2.2 times more likely to have vaginal sex than thise who didn't sext, according to the study.

One expert told HealthDay that the age at which this behavior is occurring may be surprising to many.

"Parents probably don't think about sexual behavior as much in 12- or 13-year-olds," said Dr. Hina Talib, an attending physician in the division of adolescent medicine at The Children's Hospital at Montefiore in New York City. "This study highlights that middle school-aged teens can be vulnerable, and that doctors and parents should be screening for these behaviors and talking about media safety. This group is at risk by the way they make decisions. They think they're invincible."

The findings published Monday in the journal Pediatrics.