Thousands of young people are going to be surveyed on their use of drugs and alcohol as one element of a continuing study on children in Ireland.
They form part of phase two of the Growing up in Ireland Study, which has been tracking the progress of 20,000 children since 2006.
Those children, who are now 9, 17 and 20 year olds will be quizzed about topics including their daily lives, their diet and their emotional health.
Older children will be asked about their sexuality and risky behaviour.
