The study of almost 400,000 children shows the percentage believed to have ADHD changes significantly depending on their month of birth
Many children diagnosed with attention deficit hyperactivity disorder (ADHD) are simply immature and will grow out of it in time, a new study suggests.
The study of almost 400,000 children aged four to 17 in Taiwan shows the percentage believed to have ADHD changes significantly depending on their month of birth.
It found just 2.8% of boys born in September have the condition, compared to 4.5% born in August.
The figure also rose steadily over the school year for girls - from 0.7 to 1.2%.
The authors say that in many cases the disparity may be caused by teachers comparing the behaviour of younger children to those a lot older.
Lead author Dr Mu-Hong Chen, of the Department of Psychology at Taipei Veterans General Hospital in Taiwan, said the findings show age could be a significant factor in the diagnosis of ADHD.
"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," he said.
"Relative age, as an indicator of neurocognitive maturity, may play a crucial role in the risk of being diagnosed with ADHD and receiving ADHD medication among children and adolescents.
"Our findings emphasise the importance of considering the age of a child within a grade when diagnosing ADHD and prescribing medication to treat ADHD."
The term ADHD is often used for a collection of behavioural problems linked to poor attention span including impulsiveness, constant fidgeting and inability to concentrate.
Around 3% to 7% of British children are thought to have ADHD - around 400,000 - with many being prescribed drugs to try and improve their concentration at school.
As well as learning difficulties, many people with ADHD have other problems such as sleep disorders. The condition is normally diagnosed between the ages of three to seven.