Almost a third of Kiwi high school students have self-harmed in an attempt to manage their negative emotions or punish themselves, according to long-term research from Victoria University.
In surveys of the same 13- to 18-year-olds over a period of five years, students with stunted emotional capacities were found to be especially vulnerable.
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Their actions may include cutting, scratching or preventing wounds from healing, and were not always obvious to caregivers.
Nearly 20 percent also had suicidal tendencies at some point.
Victoria University psychology professor and survey lead Marc Wilson said some students had not learned to manage their emotions healthily.
They thus resorted to self-harm to quell their sense of detachment.
"Managing emotions was the most common function of self-injury, followed by self-punishment and the desire to feel something," Professor Wilson said.
"As expected, young people who are less well-equipped to understand and manage their emotions are more likely to manage their emotions through self-injury."
Professor Wilson said the process was a vicious cycle in which emotionally damaged students self-harm and then subsequently feel more damaged.
Some young people may ultimately rely upon self-harm for relief.
Relationships with schools, teachers, fellow pupils and family were therefore crucial in preventing acts of self-harm, the report found.
The three 30-minute surveys - each of which encompassed more than 900 students - were carried out in classrooms under supervision.
The same students were surveyed as they progressed through high school.