*The following is excerpted from an online article posted on HealthDay.
About 15 percent of teenagers say they've shared a sexually explicit image or video of themselves over the internet or via phone messaging, researchers say.
And nearly twice as many -- about 27 percent -- said they've received a "sext," either from the original sender or from someone passing it along, according to a review of 39 prior studies.
Sexting between teenagers is increasing with the widespread use of camera-equipped smartphones and computers, said Sheri Madigan, lead researcher of the new report.
Madigan said she doesn't find the study results surprising, given that 2 out of every 5 high school students engage in sexual intercourse and half of adults report that they've sexted.
"I think 15 percent of youths reporting that they're sexting isn't as surprising when you think about those other statistics," said Madigan, an assistant professor of psychology with the University of Calgary in Canada.
What's more surprising and concerning, she said, is that nearly as many teens say they've shared a sext that wasn't theirs.
"About 12 to 13 percent of kids are reporting they have forwarded on a sext to another person without consent of the sender," Madigan said. "They're forwarding on other people's sexually explicit images or videos without consent."
Teenagers don't appear to grasp the consequences of sexting, psychology experts said.
For example, they don't realize that the photos they share could wind up in others' hands, where they might be used to threaten or blackmail, Madigan said.
The 39 sexting studies that Madigan's team analyzed were conducted between 2009 and 2016. Twenty-two were done in the the United States, 12 in Europe, 2 in Australia, and 1 each in Canada, South Africa and South Korea.
"Sexting has increased over that time span, from 2009 to 2016, so it's on the rise," Madigan said.
Teens are more likely to sext as they age, the researchers found, and are more likely to use a mobile device than a computer to share their explicit self-images.
Boys and girls were equally likely to sext, Madigan said.
The new study appears Feb. 26 in JAMA Pediatrics.