Primary school children who are several months to a whole year younger than their same-year classmates are more likely to be diagnosed with attention deficit hyperactivity disorder (ADHD), according to research from the U.K.'s University of Nottingham and the University of Turku in Finland.
The scientists studied data from children born in Finland between 1991 and 2004 who were diagnosed with ADHD from age seven onwards — the age they start school. In Finland, school starts in mid-August. Therefore, the oldest children in a school year are born in January, and are seven years and seven months old, and the youngest are born in December, and are six years and seven months old.
Around five per cent of "school-age children" are affected by ADHD worldwide. On average, they are diagnosed around the age of six or seven — the age they generally start primary school — where the school environment requires them to concentrate, focus their attention and stay calm.
The study found that younger children were more likely to be diagnosed with ADHD than their older peers in the same school year — boys by 26 per cent and girls by 31 per cent.
With an age variation of up to 12 months in the same class, teachers and parents may misattribute a child's immaturity.Dr. Kapil Sayal
The study also found that for children under 10 years old, this association got stronger over time. Between 2004 and 2011, children born between May and August were 37 per cent more likely to be diagnosed with ADHD than those born between September and December, and 64 per cent more likely than oldest children, born between January and April.
The study's authors suggest that parents, teachers and clinicians involved assessing children for ADHD should bear in mind the child's "relative age" within their school year.
"With an age variation of up to 12 months in the same class, teachers and parents may misattribute a child's immaturity. This might lead to younger children in the class being more likely to be referred for an assessment for ADHD," explains Kapil Sayal, lead author of the study and Professor of Child & Adolescent Psychiatry at the University of Nottingham School of Medicine and the Institute of Mental Health in Nottingham, UK.
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