Almost one in five children aged between nine and 12 hears voices that other people cannot hear, before growing out of it.
New research from the Health Research Board suggests that 5pc of people will continue to hear voices as adults. However, the board's study reveals that the age a child stops involuntarily hearing voices provides important clues about who could benefit from support and interventions to minimise the risk of future mental health conditions.
The study by Dr Ian Kelleher, research associate professor of psychiatry at Trinity College school of medicine, shows 17pc of children hear voices in the final years of primary school.
As their brains mature, they usually grow out of this. Dr Kelleher's research shows 7pc of those aged between 13 and 18 continue to hear voices, dropping to 5pc by adulthood.
Dr Kelleher said "transient auditory hallucinations" can be a common experience in childhood development. They are different to imagined experiences, such as having an imaginary friend, because the child does not have control over when they hear the voices.
"There is something very dramatic about the idea of hearing voices but when you drill down into what is going on, it is that something is happening at perception level that is going a bit awry," he said.
"Younger brains are more likely to have this happen because of the way they are wired, and that is not necessarily something to worry about."
For instance, a 10-year-old hearing voices will not necessarily be associated with mental illness, as the child may grow out of this, he said.
"But for teenagers who displayed symptoms, it was more likely to be a marker of something going wrong with their mental health. About three quarters of the teenagers who reported these symptoms had at least one mental illness," Dr Kelleher said.
The study includes surveys and meetings with more than 2,000 children in Dublin, counties surrounding the capital and Cork over the past 10 years.
Dr Kelleher said hearing voices can be linked to conditions such as schizophrenia, depression, anxiety disorders, obsessive compulsive disorders and autism.
Knowing how and when a child experiences symptoms can provide early clues to help medical experts intervene appropriately.
"It is possible to assess what is going on, identifying if there is a mental illness and how to treat that specifically.
"That can be a mixture of social interventions, or medication therapy or anything in-between depending on what is appropriate for the specific illness," said Dr Kelleher, who is also a child and adolescent psychiatrist at Lucena Clinic Child and Adolescent Mental Health Service specialising in the assessment, diagnosis and treatment of mental health disorders.
He said the research should help with early diagnosis of mental health illnesses, key to improving patient outcomes.