Rising numbers of young New Zealanders are being admitted to hospital for-self harm incidents, with Māori and women over-represented.

Last year 3,081 people aged under 20 were hospitalised with self-inflicted injuries – 200 more than 2017, and 400 more than 2016, RNZ reported.

Māori accounted for 30% of admissions last year for self-harm incidents, while the “vast majority” of admissions were young women.

Youth mental health campaigners have said actual rates of self-harm will be higher as many young people do not report self-harm incidents, especially if they are ongoing.

New Zealand has one of the the highest rates of youth suicide in the developed world, and this year the Labour-Coalition government invested a record NZ$1.9bn in mental health and addiction services in the annual budget, including placing a mental health worker in every health centre and doctor’s clinic in the country.

According to KidsHealth NZ, an NGO, self-harm is becoming more common not only in New Zealand but also in western countries such as the UK, Australia and US.

It lists the most common reasons young people self-harm as “to cope with stress and anxiety, a physical demonstration of emotional pain and to feel something when they feel numb”.

Victoria University psychology professor Marc Wilson has conducted academic studies of self-harm among young New Zealanders.

“I‘ve found that between a third and a half of our young people hurt themselves before they leave school. In the international context, this is a lot – on average, about 20% of young people around the world hurt themselves,” Wilson wrote of his research.

“Sure, self-injury is a big part, but so are such things as their broader mental health, their social wellbeing and things like their experience of bullying.

“Importantly, what it is not about for most people who hurt themselves is suicide. And we know this logically, because self-injury is so much more common than attempted and completed suicide.”

Currently mental health care for young people in high schools was “variable”, prime minister Jacinda Ardern said, and research had shown that having a mental health worker stationed in high schools lowered the depression and suicide risk by two-thirds, but this service was not yet nationally available.

Counsellors at high schools have said they are overwhelmed by demand, and they are able to see only the most serious cases such as suicidal ideation.

Ardern is a passionate advocate for improving the wellbeing and mental health of children and young people, and said it had been neglected for too long, with dire consequences – including a record high number of suicides last year.

“We know there’s huge need out there for mental health support,” Ardern said in September.

The rising number of self-harm cases was “obviously concerning”, health minister David Clark told the Guardian.

Clark said the half a billion dollars had been dedicated to frontline mental health services and these would be available to young people with mild to moderate mental health issues in “youth one stop shops”, as well as Iwi and doctor’s clinics.

“Young people who are at risk of self-harming are exactly the sort of people that these services are intended to help,” Clark said.

Currently, access to mental health support for young people varies widely around the country. Free services are available for youth in quake-struck Canterbury and Kaikoura, but in Otago, Northland, the Hawke’s Bay and other rural provinces, waiting lists remain months long, and private services are prohibitive for most families, costing hundreds of dollars.

• For information and support in New Zealand call Lifeline on 0800 543 354 or text HELP to 4357, Suicide Crisis Helpline on 0508 828 865. In Australia, the crisis support service Lifeline is 13 11 14. In the UK and Ireland, Samaritans can be contacted on 116 123 or email jo@samaritans.org or jo@samaritans.ie. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. Other international helplines can be found at www.befrienders.org.