Youngest children in class 'more likely to be given ADHD drugs'

"Youngest children in class more likely to get ADHD medication, study says," The Guardian reports.

The results of an Australian study have caused concerns that, in some cases, immature behaviour may be misinterpreted as evidence of a behavioural disorder.

In a brief report, researchers found nearly 2% of 6-15-year-olds in Western Australia received a prescription for attention deficit hyperactivity disorder (ADHD) medication in 2013.

Those born in the last months of the school year intake were more likely to have had a prescription than the oldest children in the year.

The gap between the oldest and youngest children in the class had a small, but significant, association with the increased use of ADHD medications. The researchers say their findings compare with those of other international studies.

It's possible the youngest children in a school year may find it harder to keep up in lessons than children almost a year older than them, and may be more likely to have problems with concentration. 

But it would be a big assumption to say ADHD is being overdiagnosed and overtreated on the grounds of this study alone.

The use of ADHD medication for under-16s in the UK is far lower than in many other developed nations – 0.4%, compared with Australia's 1.9% or the US' 4.4% – so the potential problem of inappropriate treatment may not be as much of an issue in this country. 

Where did the story come from?

The report was authored by four researchers from Curtin University, Murdoch University and the University of Western Australia, all in Australia.

The study was published in the peer-reviewed Medical Journal of Australia, and the researchers declared no conflict of interest or study funding.

It's available to read online on an open access basis, so you can download the study for free.

The UK media coverage was accurate, but does not point out the limitations of this brief report.

What kind of research was this?

In this brief one-page report, the researchers say four international studies found the youngest children in a school year are more likely to be receiving ADHD medication.

They aimed to see how Western Australia compares by analysing data from the Pharmaceutical Benefits Scheme – a scheme similar to the NHS, where the cost of medicine is subsidised by the Australian government – to see how many children were receiving ADHD medication.

This brief report provides very limited information about the authors' methods, making it difficult to critique.

And we don't know how the authors identified the four international studies they reported, so we don't know whether this is a fully comprehensive look at the subject.

This means the report must largely be considered to be the opinion of its authors. 

What did the researchers do?

The researchers compared the proportion of children born in the first and last months of a "recommended school year intake" who were recorded in the Pharmaceutical Benefits Scheme as receiving at least one prescription for ADHD medication in 2013.

The study included a total of 311,384 children, covering two age bands: those aged 6-10 (born July 2003 to June 2008) and those aged 11-15 (born July 1998 to June 2003).

The researchers looked at the number of children receiving medication and the patterns by time of birth. 

What did they find?

The researchers found 1.9% of the full study sample (5,937 children) had received at least one prescription of ADHD medication, with more boys than girls being prescribed for (2.9% versus 0.8%).

In the 6-10-year-olds, they found those born in the last month of the school year intake (June) were nearly twice as likely to have been prescribed medication as those born in the first month (the previous July): relative risk (RR) 1.93 for boys (95% confidence interval [CI] 1.53 to 2.38) and RR 2.11 for girls (95% CI 1.57 to 2.53)

The same pattern was seen for 11-15-year-olds, but the risk increase was less, though still significant (RR 1.26, 95% CI 1.03 to 1.52 for boys; RR 1.43, 95% CI 1.15 to 1.76 for girls).

The authors say similar effects were also seen when comparing those in the first three to six months of intake with the last three to six months.

What did the researchers conclude?

The researchers say at 1.9%, their observed prescription rate is comparable to a recent Taiwanese study, and both this study and three North American studies observed the effects of birth month on prescription rates.

They describe a professional from the American Psychiatric Association who feels ADHD is overdiagnosed and overmedicated, saying that, "Developmental immaturity is mislabelled as a mental disorder and unnecessarily treated with stimulant medication."

The authors say the findings indicate that, "Even at relatively low rates of prescribing, there are significant concerns about the validity of ADHD as a diagnosis." 

Conclusion

Overall, this study suggests that in Western Australia – and reportedly in other countries, too – the youngest children in a given school year are more likely to be diagnosed with and treated for ADHD than the eldest in the year.

However, it's important not to draw too many conclusions from this brief report. The authors provide very limited information about their methods, so it's not possible to critique how they conducted their study.

We don't know why they selected the 2013 school year, for example. It was said to be recommended, but we don't know why. It could be it was known there were an unusually high number of prescriptions noted in the Pharmaceutical Benefits Scheme that year, which means it might not be representative.

Also, this database can only tell us the number of children that filled out at least one prescription for ADHD medication. We don't know how the children were diagnosed, how long they had been diagnosed or treated for, or whether they actually took the medication.

The authors also point out the possible limitation that they didn't know how many children may have entered school outside of their recommended starting year – although this was thought to be few.

We also don't know how the researchers identified the international studies, and we don't know that these reported findings give a comprehensive look at ADHD diagnosis and treatment worldwide.

It would be a big assumption to say ADHD is being overdiagnosed and overtreated on the grounds of this study alone. And, as no UK studies were reported, we don't know what the true situation is like in this country.

It's possible the youngest children in a school year may find it harder to keep up with lessons than children almost a year older than them, and so could be more likely to be distracted – though this is clearly a big generalisation and is not always going to be the case.

However, it does perhaps highlight there is a need for children who are struggling or finding it difficult to concentrate at school to be recognised, and get the additional attention and support they need – something both teachers and parents of the youngest children in a school year may need to be aware of.