Children aged between 11 years to 13 years tend to hear strange voices, according to a new report.

Researchers from the Royal College of Surgeons in Ireland have discovered that auditory hallucinations (hearing voices) can affect up to one-in-five children between the ages of 11 to 13.

"We found that auditory hallucinations were common even in children as young as 11 years old. Auditory hallucinations can vary from hearing an isolated sentence now and then, to hearing "conversations" between two or more people lasting for a several minutes. It may present like screaming or shouting and other times it could sound like whispers or murmurs. It varies greatly from child to child, and frequency can be once a month to once every day," said Dr Ian Kelleher, professor at the Royal College of Surgeons, in a statement.

Researchers had conducted four separate studies on 2,500 children, aged between 11 and 16 years. They found that 20 to 23 percent of younger adults, aged 11 years to 13 had experienced auditory hallucinations. Among them more than 57 percent have mental disorders.

In older adolescents (aged 13-16 years), just 7 percent reported hearing voices. However, among this category, more than 80 percent had psychiatric disorder - showing a clear association between auditory hallucinations and serious mental illness.

In several children, these experiences appear to represent a 'blip' on the radar that does not turn out to signify any underlying or undiagnosed problem.

However, for the other children, these symptoms turned out to be a warning sign of serious underlying psychiatric illness, including clinical depression and behavioural disorders, like attention deficit hyperactivity disorder.

Some older children with auditory hallucinations had two or more disorders.

It is a significant finding which can help the doctors to consider more than one diagnosis, if the child reports auditory hallucinations.

Our study suggests that hearing voices seems to be more common in children than was previously thought. In most cases these experiences resolve with time. However in some children these experiences persist into older adolescence and this seems to be an indicator that they may have a complex mental health issue and require more in-depth assessment," said Mary Cannon,professor at the Royal College of Surgeons, in a statement.