Children diagnosed with attention deficit hyperactivity disorder (ADHD) may just be "immature" compared to their school peers, a new study has suggested.
Researchers found the percentage of children diagnosed with ADHD significantly changes depending on their month of birth - 2.8% of boys born in September were diagnosed with the condition, but the figure increased to 4.5% for those born in August.
The study called 'ADHD or just immature?', published in the Journal of Pediatrics, looked at nearly 400,000 children between four and 17 years old in Taiwan.
Children who were born in August were more likely to be diagnosed with ADHD
For girls in the study, the percentage rose from 0.7% of those born in September to 1.2% with August birthdays.
"Our findings emphasise the importance of considering the age of a child within a grade when diagnosing ADHD and prescribing medication to treat ADHD," said Dr Mu-Hong Chen, lead author of the study.
The NHS states symptoms of ADHD in children include a short attention span or being easily distracted, restlessness, constant fidgeting or overactivity and being impulsive.
When broken down and analysed according to age, nursery or primary school-aged children born in August had an increased risk of being diagnosed with ADHD and receiving ADHD medication.
However, teenagers born in August did not have an increased risk of ADHD diagnosis. Study authors said this implied that increasing age and maturity lessens the impact of birth month on ADHD diagnoses.
The authors concluded that teachers may be comparing behaviour of the more mature children born in September, to the younger children who are nearly a year younger.
Percentages of boys with ADHD compared to birth month
September - 2.8
October - 2.8
November - 3.1
December - 3.1
January - 3.5
February - 3.4
March - 3.9
April - 3.9
May - 3.9
June - 4.1
July - 4.2
August - 4.5
Dr Chen added: "When looking at the database as a whole, children born in August were more likely to be diagnosed with ADHD and/or receive ADHD medication than those born in September.
Dr Kuben Naidoo, consultant psychiatrist and chairman of the ADHD Foundation, said although the findings of the study were interesting, they must be treated with a "degree of caution".
"The authors have stressed that they conducted this study to determine if findings in an Asian population mirrored results from earlier work carried out in Western populations," he said.
"These earlier studies did in fact confirm the potential influence of relative age on the diagnosis and treatment of ADHD in children and adolescents.
"While the study findings indicate an increase in the rate of diagnosis and treatment for ADHD in this Taiwanese population, the authors acknowledge significant limitations including absence of key information such as family history and environmental factors."
Dr Naidoo said the study highlights the importance of ensuring the assessment for ADHD is rigorous and relies on a variety of sources of information.
He said in the UK, the assessment and diagnosis of ADHD across the lifespan is "robust" and relies on information gathered from a number of sources including the family and school.
"The option to treat with medication is not taken lightly and consideration is also given to psychological strategies to support the individual," he added.
"The issue is not as simple as assuming that age, as an indicator of neurocognitive maturity, influences ADHD symptoms as we do see a significant number of adults presenting to psychiatric services for the first time with symptoms of ADHD."
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