In a separate study, Mitchell and her colleagues also found that in 2008 and 2009, law enforcement officials across the country investigated about 3,500 cases of sexual images created by teens. Of these cases, most arrests occurred in cases in which sexting violated child pornography laws or when there was another crime involved, such as blackmail or harassment. More than 80 percent of the images remained on mobile phones and did not end up online.
"We need to look at these on a case by case basis since there are such a variety of images," Mitchell said. A lot of the behavior, she explained, is merely the result of adolescent experimentation or curiosity. In general, arrests aren't the norm unless there are adults involved in the sexting.
Regardless of the observed decline in sexting among youth and the fact that a lot of the behavior may only be sexual experimentation, Mitchell emphasized that young people need to be aware of the risks involved with the exchange of sexually suggestive material.
"It's important for teens to be aware of what they're doing," Mitchell said. "Because of the nature of technology, they can't expect it to stay with the person they send it to. It can be circulated and can be embarrassing." In some cases, it can be treated as a crime, so young people should be aware of those repercussions as well.
It can also be emotionally devastating. In the study of the Boston-area high school students, researchers found that students involved in sexting were more likely to report attempting suicide and were twice as likely to report depressive symptoms.
ABC News' Christina Caron contributed reporting to this story.