As early as third grade, some children are hitting, cutting or otherwise hurting themselves, according to new research.

Studies have suggested about one-fifth of teens and young adults engage in self-injury at some point to relieve negative emotions or reach out for help, for example. But this report is the first to ask the question of kids as young as seven. Researchers found one in 12 of the third-, sixth- and ninth-graders they interviewed had self-injured at least once without the intention of killing themselves.

"A lot of people tend to think that school-aged children, they're happy, they don't have a lot to worry about," said Benjamin Hankin, a psychologist from the University of Denver who worked on the study. "Clearly a lot more kids are doing this than people have known."

Hankin and his colleagues spoke with 665 youth about their thoughts and behaviors related to self-harm. They found close to eight percent of third graders, four percent of sixth graders and 13 percent of ninth graders had hit, cut, burned or otherwise purposefully injured themselves at least once. In younger kids hitting was the most common form of self-injury, whereas high schoolers were most likely to cut or carve their skin.

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