STRESSED: Nearly 20,000 children and teenagers are on anti-depressants.

More children are being medicated for mental disorders than ever - with clinicians blaming the stress of being a modern-day teenager.

The latest available figures, released to The Dominion Post under the Official Information Act, show nearly 20,000 children and teenagers were on anti-depressants in 2013.

The number has climbed every year since 2009, and early signs from last year suggest the increasing tendency to medicate mentally troubled kids will continue.

The use of anti-psychotics, once reserved for severe psychosis, is also at record levels, being prescribed to treat everything from autism to sleeping difficulties.

Anti-psychotics are even being used on a small handful of children under 4 to treat "severe behavioural difficulties".

A child health expert said the rise was partly down to improved access to drugs, but it also reflected a more anxious generation of children, who faced pressures unknown to their parents.

Sue Bagshaw, a Christchurch clinician who studies and treats mentally ill youth, said children and teenagers today were more likely to have busy and separated parents, higher expectations of academic and social success, and were constantly being bombarded with information through online connected devices.

"We are absolutely overloading them," she said.

While improved access to medication was helpful, it had not been matched with better access to other talking-based therapies, undermining its effectiveness.

Drugs were sometimes inappropriately prescribed, with grief, frustration or loneliness labelled as depression.

"Very often they're just given a pill and told to get on with it."

Masterton mother Toni Ryan, whose depressed 16-year-old son Sam killed himself in 2011, now offers informal counselling and referral services to other mentally troubled teens.

She said many of the teens she saw were being prescribed anti-depressants and other medication by their doctors without their parents' knowledge, and were struggling with support. That was potentially dangerous because some medication could make them feel worse before they felt better.

Child psychiatrist Liam O'Connor, who works for Capital & Coast DHB, said there was some evidence, although limited, of higher rates of mental illness in the current generation of adolescents and teenagers. "We have seen an increase with adolescents and girls especially."

Arran Culver, the Ministry of Health's deputy director of mental health, said the increase in medication was roughly in line with more kids being seen by mental health specialists, with access rising by about 35 per cent since 2009.

There was no firm evidence of how many under-19s had mental health problems in New Zealand, but overseas studies suggested it could be about one in 10.

Most would not need specialist help but 3 per cent would need intervention, which roughly equated to how many were being treated now.

"I think there is a risk with alarmist messages around medication, but the risks of untreated adolescent depression can be very high."

There was not enough research to determine whether demand for mental health services was increasing among teens and children, or whether the rise simply reflected better access to those services, he said.