Younger children in a school class at greater risk of long-term negative outcomes like low educational achievement and substance misuse

New research from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London, in collaboration with the Karolinska Institute and Orebro University, has found that ‘young relative age’ – being young in a school class – puts a child at a long-term disadvantage compared to their older peers.  Researchers are now calling for greater flexibility about school starting age.

The study, published today in the Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP), looked at data from 300,000 individuals from the Swedish National Registers. The researchers found those youngest in a class were more likely to experience low educational achievement, substance misuse disorder, and depression in later life. However, younger children with ADHD appeared less at risk of depression. 

Previous studies have pointed to evidence that immaturity relative to peers can contribute to an increased likelihood of being diagnosed with ADHD. Typically, a comparison is made as to whether a child shows ADHD symptoms to a significantly greater degree than to others in their year group, but this doesn’t always take in to account the potentially significant age gap between the youngest and oldest members of an age group.

Senior author Professor Jonna Kuntsi from King’s IoPPN said “The difference between the youngest and oldest member of a class can be up to 11 months. In the early stages of childhood, this is a significant difference in terms of maturity, behaviour and cognitive abilities.

“Behavioural characteristics that are normal in younger children are in some cases being compared to much older individuals, and we can see from the data that there are very real and long-term consequences to being the youngest in a class year.”

The investigators note that the negative effects of young relative age is much less common in countries like Denmark, possibly due to the more flexible approach to school starting age there.  Young children that might not be ready to start school have the opportunity to start school later, and as such are at less risk of experiencing negative side effects seen in other countries. It is a practice that the researchers say could be emulated elsewhere.

Professor Kuntsi has previously called for greater focus to be placed on the relative age of students in relation to difficulties with reading, spelling or arithmetic skills which aren’t as a result of low cognitive ability. A recent large register study in Finland found that the relative age effect emerges also for specific learning disorders which Professor Kuntsi says is likely due to the same referral bias as those referred for ADHD assessment.

She cites a need for a cross-country review into approaches that best ensure children’s future outcomes are fully independent of their relative age at the start of school: “Being the youngest child in a classroom can have complex developmental consequences, and can place them at a disadvantage at the earliest stages of their academic life. If we are to overcome this, there needs to be a greater understanding from decision makers, teachers, and clinicians so that all children have an equal chance to succeed later in life.”

King’s IoPPN, in partnership with the South London and Maudsley NHS Foundation Trust and the Maudsley Charity, are in the process of opening a world leading centre for children and young people mental health. The Pears Maudsley Centre for Children and Young People is expected to open in 2023 and will bring together researchers and clinicians to help find solutions that will transform the landscape for children’s mental health.

This study was possible thanks to funding from funding from the European Commission’s Horizon 2020 research and innovation programme under grant agreement No 667302, and the from the Swedish Council for Health, Working Life and Welfare.

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For further information, please contact Patrick O’Brien, Senior Media Officer at Patrick.1.obrien@kcl.ac.uk.

The combined effects of young relative age and ADHD on negative long-term outcomes (DOI 10.1016/j.jaac.2021.07.002) (Kuntsi J PhD, Larsson H PhD, Deng Q MSc, Lichtenstein P PhD & Chang Z PhD) was published in the Journal of the American Academy of Child and Adolescent Psychiatry.

About King’s College London and the Institute of Psychiatry, Psychology & Neuroscience

King’s College London is one of the top 10 UK universities in the world (QS World University Rankings, 2018/19) and among the oldest in England. King’s has more than 31,000 students (including more than 12,800 postgraduates) from some 150 countries worldwide, and some 8,500 staff.

The Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London is the premier centre for mental health and related neurosciences research in Europe. It produces more highly cited outputs (top 1% citations) on mental health than any other centre (SciVal 2019) and on this metric we have risen from 16th (2014) to 4th (2019) in the world for highly cited neuroscience outputs. World-leading research from the IoPPN has made, and continues to make, an impact on how we understand, prevent and treat mental illness and other conditions that affect the brain.  https://www.kcl.ac.uk/ioppn @KingsIoPPN