Four in ten 17-year-olds have not spoken to their parents about sex and relationships, research has found.
In a joint research programme, the Economic and Social Research Institute (ESRI) and the HSE analysed how young people receive information on sex and relationships.
Using data from the Growing up in Ireland '98 cohort at 13 and 17 years of age, the research also examines the role of this information in shaping sexual behaviours among Irish adolescents.
Among the key findings include that at age 13, just over half of young people reported that they had received relationships and sexuality education (RSE) at school, and this proportion had increased to 92% by age 17.
There was significant variation in RSE receipt across individual second-level schools, supporting previous Irish research that finds that policy and leadership at the school level plays an important role in the timing of RSE provision.
At age 13, 45% of young people reported that they had discussed sex and relationship issues with their parents.
By age 17, this proportion had increased to just under 60%. Young people who had better-quality relationships with their parents were more likely to talk to them about sex and relationships, the research also found.
There was a clear gender divide in reports of ease of discussions with parents about sex with young women finding it easier to talk to their mothers, while young men found it easier to talk to their fathers.
But nearly 60% of young men still found it difficult or very difficult to talk to their fathers about sex.
At age 13, parents and family were the main source of information about sex, but at age 17, friends were the most commonly cited source.
At age 17, nearly a quarter of young men and 20% of young women cited the internet, TV, films, books as their main source.
Those who had poor-quality relationships with their peers were much more likely to rely on information from the same sources.
On Tuesday the Minister of State with responsibility for Public Health Frank Feighan launched the ESRI/HSE research report 'Talking about Sex and Sexual Behaviour among Young People in Ireland'.
Anne Nolan, a co-author of the report, said: "The study findings show us that the quality of the relationship between parents and their children is a key determinant of whether discussions about sex and relationships take place and how easy young people find it to speak to their parents about sex.
"Initiatives to support parents in developing positive communication skills may be expected to have broader benefits in terms of discussions about sex and relationships."
Emer Smyth, a co-author of the report, said: "A significant group of young people are not receiving information or advice on sex from their parents, making school-based relationships and sexuality education all the more important.
"The findings support the current move towards considering sexual wellbeing as part of broader school efforts to support young people's wellbeing."
Minister Feighan said: "Evidence based information is vital to understanding emerging trends in sexual health and to ensuring that the support we are providing for parents, children and young people have a firm foundation.
"I have no doubt that this study will make a very welcome contribution to our knowledge base here."