A significant number of lesbian, gay, bisexual and transgender people in Ireland aged 25 and under experience severe stress, anxiety and depression, according to a new report.
The study found that over half of 14 to 18-year-olds had self-harmed, 70% had suicidal thoughts and one in three had attempted suicide.
The report has been published by the Gay and Lesbian Equality Network (GLEN) and BeLonG to Youth Services.
The research, which was funded by the HSE national office for suicide prevention, reveals that LGBT people still experience bullying at school, fear of rejection and discrimination, violence and negative attitudes.
Research was carried out using online surveys of more than 2,600 people as well as a survey of 1,000 people to assess public attitudes.
It found the most common age people discover their LGBT identity is 12 but it is another four years before they tell the first person of their sexual identity.
One in four had not told their parents that they are LGBT.
Meanwhile 3% had not come out to anybody with fear of rejection and discrimination – one of the main reasons they continued to conceal their identity.
The fear of rejection was strong where there was an awareness of negative attitudes within their family or among friends.
Launching the report former president Dr Mary McAleese said the problems are at their worst in second-level schools.
She said while there is some evidence of positive changes in LGBT experiences in schools, the sad reality is there are significant numbers of very sad and fearful teenagers afraid to go to school.
She added they are afraid of being picked on because of their sexual orientation, uncomfortable and full of dread.
She that the study was essential reading and revealing as it is horrifying.
Dr McAleese said Ireland's universities, colleges and workplaces were regarded as safe and welcoming places for the LGBT community and there was some evidence that thanks to more open debates on sexual identity in Irish society, schools were beginning to make inroads into anti-LGBT bullying.
GLEN director of mental health Odhrán Allen said he was disappointed to see the level of distress among LGBT teenagers and the survey reflects a very serious problem.
Speaking on RTÉ's Morning Ireland, Mr Allen said that in particular bullying in school was a widespread problem.
He said that despite the progress made in Ireland, LGBT teenagers feared rejection from family and friends.