Some 21% of young adults between the ages of 17 and 25 say they have engaged in self-harm.
A report by Headstrong launched today shows that depression, anxiety and stress gradually increase in secondary school students from first year to sixth year.
The report, which details the mental health and well-being of Irish young people between the ages of 12 and 25 for the first time, also found that 41% of young adults wre in the "problem-drinking" range.
For young adults, specifically, strong links were found between excessive drinking and suicidal behaviour.
The survey collates the views of 14,306 young people aged 12-25 years.
Director of research at Headstrong Barbara Dooley said young adults engaging in self-harm did not talk about their problems.