People attended Northern Ireland emergency departments 12,000 times last year because of self-harm or suicidal thoughts, research revealed.
Images of self-harming have been shared on social media sites, campaigners warned, the physical pain helping young people cope with emotional pain.
Almost a third of patients were in the Belfast health and social care trust, the largest in the country. Health minister Jim Wells said those who sought medical attention were thought to represent only the tip of the iceberg.
He added: "Sadly, many will not seek help at all."
The Northern Ireland Registry of Self-Harm Annual Report 2013/14 is an analysis of the prevalence of self-harm presentations to the 12 local emergency departments of Northern Ireland's hospitals.
It said the total numbers of presentations in Northern Ireland for self-harm and suicidal ideation for the financial year 2013/14 was 12,076.
There were 8,453 self-harm presentations to emergency departments in Northern Ireland, involving 5,983 people.
Mairead Monds, the ChildLine charity's services manager in Northern Ireland, said sharing images of self-harm on social media sites was a worrying new development, especially among such a young age group of children.
"There are many reasons why young people might self-harm. It's a way of dealing with overwhelming feelings that can feel very difficult to cope with and young people tell us that physical pain helps them cope with the emotional pain."
During 2013-2014, counsellors at the ChildLine bases in Belfast and Foyle received 2,622 contacts either on the telephone or online from children and young people across the UK about self-harm.
One young person who contacted a counsellor at the ChildLine base in Belfast said: "I've been suffering with depression for years but recently it's got so much worse. I feel like I'm slipping back into a dark place and I don't know how to escape it. It's making me really anxious. I don't know what to do."
The purpose of the registry is to improve understanding about self-harm and related behaviours in Northern Ireland and to help shape the development of services and support to meet the need represented by the registry.
The report is being launched at the 2015 Self-Harm Symposium: A Global Challenge.
Mary Black, Public Health Agency (PHA) assistant director, said: "The publication of the second annual report is timely, with the forthcoming launch of the next suicide prevention strategy for Northern Ireland (2015-20) and the commissioning by the PHA of new self-harm community-based support services.
"There has been concerted effort to increase our understanding of the issues represented in the data, and perhaps more importantly, what can be done to raise greater awareness about the issue of self-harm, supporting carers and families and informing professionals working in this field in both the community and statutory sectors."