IRISH young people have higher rates of mental health difficulties than their peers in Europe and the USA, with more than half suffering a significant problem by the age of 24.
The mental disorder could involve a young person experiencing a behavioural or psychological problem either causing them distress or anxiety, such as a bereavement.
More seriously, it could see the young person suffering from a mood disorder such as depression, experiencing psychosis, or having suicidal thoughts.
By their mid-20s, nearly 75pc have engaged in binge drinking, with one in five meeting the criteria for mental health problems linked to this behaviour at some time in their lives.
The findings from research by the Royal College of Surgeons in Ireland (RCSI) showed one in five young Irish adults aged 19-24 and one in six young people aged 11-13 are experiencing mental disorder.
The 'Mental Health Of Young People in Ireland' report pointed out that suffering psychological stress in early life leaves young people at increased risk during their adult years.
Professor Mary Cannon of the RCSI said: "Our research shows that high numbers of teenagers and young adults in Ireland are experiencing mental ill-health at any given time.
"For the first time in Ireland, we have evidence. . . that young people who experience mental ill-health during adolescence have higher rates of mental disorders and substance misuse during their young adult years."
High numbers of young adults aged 19-24 engaged in the misuse of alcohol and drugs, according to the findings of the RCSI Psychiatric Epidemiology Research across the Lifespan (PERL) Group.
"Of particular concern is that three out of four young adults met lifetime criteria for binge drinking. The research also reveals that almost one in five (19pc) had thought about suicide," said Prof Cannon.
The research involved surveying and interviewing more than 400 people between the ages of 11 and 24. It is the first time such comprehensive data about disorders among young people in Ireland was published.
"Our research points to high levels of self-injurious behaviour and suicidal thoughts among Irish youth," she said.
"For young adults, just under one in 10 had engaged in deliberate self-harm and one in five experienced suicidal thoughts.
"Both of our studies (found) many of the young people who were experiencing mental health difficulties had not sought help," Prof Cannon added.
"We found that experiences of family discord, intimate relationship abuse and stress related to death, health, work and relationships were implicated in young people's risk of experiencing a mental disorder.
"We also found that being of a minority sexual orientation was associated with mental ill-health among young adults."
The report was launched by Junior Health Minister Kathleen Lynch.
She said: "I would appeal to any young person who thinks they may have a mental health issue not to suffer in silence and to seek help."
How I got over depression: Pages 34 & 35