Teenagers are in urgent need of extra support to help them cope with stress during high school, says Mission Australia CEO Catherine Yeomans.

A new report shows almost one in four young Australians meet the criteria for a probable serious mental illness.

The Mission Australia and Black Dog Institute joint report, released on Wednesday, shows the number of teens aged 15-19 in psychological distress has risen significantly, up from 22.5 per cent in 2012 to 28.6 per cent in 2016.

And girls are suffering the most, twice as likely than boys of the same age to report high psychological distress - 28.6 per cent compared to 14.1 per cent.

Coping with stress, school, study problems, body image and family conflict were the main areas of concerns among those in distress.

Mission Australia CEO Catherine Yeomans says if extra support isn't given to teens during this challenging time their mental health will only deteriorate.

"We are talking about an alarming number of young people facing serious mental illness, often in silence," said Ms Yeomans.

"Parents, schools and community all play a vital role and we must fully equip them with the knowledge and skills to provide effective support to young people."