New research has found children who owned a mobile phone at age nine performed worse in tests at age 13.

That is according to new ESRI research funded by the Department of Communications and the Commission on Communications Regulation (ComReg).

The research used data from 8,500 children in the 'Growing Up in Ireland' study to examine the academic performance of children who owned a mobile phone at an earlier age.

It found children who owned a mobile phone at age nine scored 4% less on average in standardised reading and maths tests at age 13.

The research found that 40% of children owned a mobile phone by the age of nine.

Children attending more socially disadvantaged schools are more likely to have mobile phones.

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Children with parents who have higher incomes and higher levels of education are less likely to own their own mobile phones at age nine.

It found an observed association between mobile phone ownership and test scores remained when factors which usually influence test scores - such as socio-economic class - were taken into account.

The ESRI said: "As schools have recently been consulting with their staff, students and parents on the place of personal devices in the school setting, these results may help schools in making decisions on whether and when to restrict access to personal devices, particularly during the primary school years."

Selina McCoy is an associate research professor at the ESRI.

She said: "This is the first time the ESRI has looked at the impact of mobile phone ownership on children's academic development.

"It is important to keep monitoring this going forward in order to provide evidence for the growing debate about the potential effects of screen time and mobile phone use of young people in Ireland".