"Even the ones that say they are just doing it because the other kids are doing it, in every single case in my study they might say that, but they also said they have other things going on - they all said there were emotional reasons going on underneath."
Dr James said the behaviour appeared glorified by some subcultures but was present amongst a large cross-section of students, including those who identified as "popular".
Dr James' research comes as University of Auckland senior pediatrics lecturer Dr Simon Denny calls for more support for young New Zealanders.
Dr Denny headed a study of adolescent health concerns published in the Journal of Paediatrics and Child Health last month. It found that 21 per cent of the 9422 Kiwi teens surveyed were engaging in risky behaviours, were distressed, or both.
Riskier behaviour was happening in clusters, and students needed better access to comprehensive health assessments from the primary health sector, he said.
Youthline CEO Stephen Bell said self-harm had become a common coping mechanism for young people and it was important they knew how to get help and felt comfortable doing so.
"Anecdotally...it is a little bit more apparent. In the day to day conversations it's moved a bit more towards the line of being normal behaviour, which is scary.
"There's a few thing we are trying to do that is every young person knows where to get help it doesn't matter if it's friends, family, other services or us - it's just that they know.
"It's not so much that there aren't places to go to get support, it's that there's a huge barrier and young people stand out as being reluctant to engage with health services and even more reluctant to engage with mental health services."
The figures:
• Survey of 387 girls aged 13 to 16 from five decile 9 and 10 Auckland schools
• 84 were identified as self-harmers
• 23 percent of self-harmers had done so in front of others
• Nearly 12 percent of self-harmers had done so with another person
• Every person who admitted to self-harm - even those who said they were influenced by others - cited deeper emotional reasons
Where to get help:
• Youthline: Support for young people and their families, Youthline.co.nz, 0800 376 633
• Kidsline: Phone counselling for children aged 9 to 13, Kidsline.org.nz, 0800 543 754 (4-6pm weekdays)
• Whatsup: Counselling for children aged 5-18, Whatsup.co.nz, 0800 942 8787 (noon to midnight)
• The Word: Questions answered about sex, life and relationships: Theword.org.nz
• Depression helpline: Counsellors who can find the right support for you, Depression.org.nz, 0800 111 757 (8am to midnight)
• Rainbow Youth: Support for young gay people Rainbowyouth.org.nz
In an emergency and you or someone else is at risk, call 111