A fifth of young Australians mentally ill

One in five young Australians are dealing with mental illness, with girls nearly twice as likely to suffer.

But more than 60 per cent of those young people experiencing mental illness feel uncomfortable getting professional help, according to a new report by Mission Australia and the Black Dog Institute.

The study of 15- to 19-year-olds across the country found 21 per cent of the 15,000 surveyed were battling a probable mental illness.

The rate among females in that age group was much higher than in young men - at 26 per cent compared with 14 per cent.

Aboriginal and Torres Strait Islanders, and young people with a disability were also more likely to be experiencing mental illness.

However, less than 40 per cent felt comfortable seeking information, advice or support from community agencies, online counselling or telephone hotlines.

"The confronting findings in this report illustrate the significant challenges many of our young people are facing when it comes to psychological distress and mental health issues," Mission Australia CEO Catherine Yeomans said in a statement on Wednesday.

"We know that many of our youth are struggling with complex issues, and it's impacting on their ability to transition with confidence into adulthood."

Ms Yeomans said early intervention and support is critical to help those vulnerable.

The Youth Mental Health Report was based on a survey that asked respondents to answer questions about their experiences of anxiety and depressive symptoms over a period of four weeks.

It will be officially launched by the NSW Mental Health Commissioner John Feneley on Wednesday.