Canterbury's mental health funding is set to be cut despite growing need among children after the earthquakes.

Canterbury's cash-strapped health authority may be forced to cut mental health services, despite evidence the region's youth are more distressed than ever before.

Funding information for the Canterbury District Health Board's (CDHB) upcoming financial year, obtained by Stuff, shows the discrepancy between the region's mental health funding and the national average growing larger.

Canterbury health bosses have vented their frustration over the issue to central government, warning some services were "running very close to the wind".

The CDHB's funding for mental health in 2015/16 was $222 per head of population, while the national average was $243. For the coming year, the Canterbury figure is expected to drop by $15 per person, while the national average will increase by about $10.

CDHB planning and funding manager Carolyn Gullery said while people were likely to be "set back" after Sunday's earthquake, there had been a plateau in adult access rates. The same could not be said for the city's children.

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"We think it's going to get worse," Gullery said.

"We're particularly worried about the kids."

Three Christchurch schools remained shut on Monday while they were checked for damage and dozens of anxious children were kept home.

However, the Ministry of Health continues to argue Canterbury's access rates for mental health were low pre-quake and money can be found within their current funding.

An article published in the Australian and New Zealand Journal of Psychiatry in 2015 showed anti-depressant and anxiety medication use high and steadily rising in Canterbury well before the earthquakes. While the CDHB served about 11.5 per cent of New Zealand's population, the region was consuming almost 17 per cent of the country's anti-depressants, 13 per cent of sedatives and hypnotics and almost 16 per cent of anti-psychotics in September 2010. All spiked after each of the earthquakes.

Should the CDHB overspend on mental health, the money would need to be pulled from other services, Gullery said. This would happen this year if the current funding package went ahead.

CDHB chief executive David Meates, chief medical officer Nigel Millar, and board chair Murray Cleverley appeared in front of the health select committee at Parliament last week, where discussions around their financial position became heated.

Meates argued the situation in Canterbury was not sustainable, and that the health system was "running very close to the wind on a number of services" and at risk of "starting to implode".

"This is not an issue of pleading poverty or whatever, what it is sitting back and saying is we are not in a business as usual environment and we have an unprecedented range of issues"

Millar nearly lost his cool during the exchange, stating: "We struggle to find four years later, having to prove that we have an increased demand . . when it is universal after a disaster. We should not have to demonstrate that."

Though National Health Board acting national director Michael Hundleby refused to answer questions on the CDHB's funding, he said "for a very small number of DHBs their percentage share of overall funding reduces, but not the actual funding they receive".

"Demand for mental health services in Canterbury [is] around the national average," he said.

"However, before the earthquakes demand for mental health services were below national average, so the ministry recognises there has been a steep increase which the DHB has had to adjust to."

Canterbury's overall funding increase for the last financial year was 1.49 per cent, compared to a national increase of 2.41 per cent.

HOW TO TO GET HELP:

* Call your GP

* Practise the Mental Health Foundation's Five Ways to Wellbeing

* Do physical exercise

* Call the Ministry of Social Development's Canterbury Support Line on 0800 777 846