Prime Minister Jacinda Ardern is calling for more research into the mental health crisis in response to revelations of a rising tide of psychological problems among young Kiwis.

Ardern told AM that New Zealanders were not alone in the issue, and that it had become a "global phenomena".

This comes after a NZ Herald Great Minds feature revealed the harrowing story of Auckland teenager Cassandra Fausett, who for two years endured a devastating spiral into mental illness leading to her death in 2019.

In the weeks after her death, Cassandra's mum Caroline began to review the journey she took through the mental health system and found that there were major problems in the system.

By Caroline's count, Cassandra had absconded 38 times in the last two years of her life. There were 17 major self-harm incidents. Twenty hospital admissions. Nine police callouts.

"When you're living it, day by day, you don't realise," she said. "But when you read it, it's like, 'Oh my God. How did I ever let Cassandra go through that?'"

"Cassandra did not receive adequate treatment + support from CAMHS [child and adolescent mental health services]," she wrote in a notebook one day as she grew angrier.

Ardern today said a worldwide shortage of mental health workers is adding pressure to the crisis.

She said the Government was already working to bring in more ability for counsellors to be accredited across different government agencies, started funding and increasing funding for youth services and putting additional counsellors and nurses into schools.

"This is not yet done; it is a growing problem and I think it's something internationally that needs to be addressed and we definitely need more research into it as well."

Meanwhile, in private briefings to Ardern, obtained by the Herald as part of an eight-month investigation into mental health care, the Ministry of Health gave a stark assessment of the ability of child and adolescent mental health services (known as "CAMHS" or "ICAMHS") to cope with a rising tide of psychological problems among young Kiwis.

Officials told Ardern the pandemic has disproportionately impacted young people and that the psychological consequences are "likely to be extensive and enduring". More children and teens are experiencing serious distress, self-harm, eating disorders, and other potentially devastating problems, they said.

"Specialist mental health and addiction services for children and youth have been under pressure for some time," a senior official wrote in May, and "data suggest[s] that the Covid-19 pandemic has increased this pressure since our September 2021 advice".

Data provided to the Prime Minister in that document showed that, across the country, CAMHS saw 49,562 people last year, down from 49,819 in 2020 and 50,207 in 2019.