New data reveals an alarming increase in young people presenting to emergency departments experiencing mental health crises.

The numbers of young people in emergency departments because of mental health crises have skyrocketed in Victoria and NSW, with experts blaming a lack of preventive treatment.

A study by the Murdoch Children's Research Institute shows a 46 per cent increase in people, aged 19 or younger, in Victorian emergency departments for mental health treatment between 2008 (5988 patients) and 2015 (8726).

A separate paper looking at NSW presentations reveals a 159 per cent increase in young people, aged 10 to 19, being treated for suicidal urges, self-harm or intentional poisoning between 2010 and 2014.

"It's extremely worrying. The emergency department, by and large, is not the place where children with mental health issues should be coming," lead author on the Victorian study, Professor Harriet Hiscock, told AAP.

Of the 52,359 mental health presentations her team looked at over seven years, more than 22 per cent were related to self-harm and a similar proportion to substance use.

About 40 per cent of young people came to hospital experiencing stress, anxiety, or mood or behavioural disorders.

Neither study, both published in the Medical Journal of Australia, looked at how many people were seeking mental health treatment for the first time and who kept returning to the emergency department.

But Prof Hiscock said the data showed "a failing in resources for these kids and their parents, and (a) failure of early prevention".

Even if families could see a clinician, many struggled to afford appointments and rebates were limited to 10 consultations a year.

"(Sometimes) they couldn't afford to go every fortnight, for example. They tried to stretch out the services for their child and that was pretty ineffective," Prof Hiscock said.

University of Melbourne and Royal Children's Hospital adolescent health expert Professor Susan Sawyer called for more and better early intervention.

"We haven't dropped the ball. We're yet to pick up the ball around a prevention agenda, particularly around self-harm," she said.

"There are some important questions to be asked about the quality of care that is being delivered in schools, as well as in the community, in terms of mental health services."

Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14.

Suicide Call Back Service 1300 659 467.

Kids Helpline 1800 55 1800 (for young people aged 5 to 25).