ADHD medication use in NZ doubled in just 10 years - study

The number of Kiwis being prescribed medicine to treat attention deficit hyperactivity disorder (ADHD) doubled in just a decade, new research has found.

In 2007 around 0.5 percent of people aged up to 24 were on medication for ADHD, compared to 1 percent in 2017.

But rather than a sign kids are being overprescribed, Stephanie D'Souza - the lead author of the new study, published in the New Zealand Medical Journal - says it's down to better diagnosis. 

"I certainly don't think it's a bad thing," she told The AM Show on Wednesday. "ADHD as a disorder itself, it's thought to be about 3 to 4 percent of young people that have it - some estimates put it a little bit higher at 5 to 6 percent."

ADHD is a neurodevelopmental disorder that is usually first detected in childhood.

"It has to do with the way that the brain functions and is wired... Symptoms are typically relating to hyperactivity and impulsivity behaviour - not being able to sit still, fidgeting a lot, talking loudly and inattentive behaviour. 

"The drugs, most of them are stimulants - there are some that aren't - they help with focus and they sort of help to temper those hyperactive impulses."

Boys are more likely to be diagnosed and receive treatment, the study found - but the increase between 2007 and 2017 was 126 percent for girls (from 0.21 to 0.49 percent) and only 83 percent for boys (from 0.8 to 1.47 percent). 

Differences were also found between ethnicities and incomes. Kids of European descent were diagnosed at the highest rates, Pasifika and Asian kids the least. Divided into quintiles, there was little difference between the richest and the middle-income areas, but those in the bottom quintile were least likely to be given medication.

Dispensing rates increased most for those in the upper income quintile.

"More deprived areas showed a smaller relative increase in dispensing prevalence," the study said. "This suggests that there may be differences in access to medication over time for different socioeconomic groups, with more deprived areas having less access."

The study concluded concerns about over-medication were overblown.

It is important to note that the dispensing prevalence at the end of our study period remained below the pooled worldwide prevalence of the disorder (3.4 percent), indicating that the medication is probably not over-dispensed. 

"However, this does not mean that medicating every child with a diagnosis of ADHD should therefore be encouraged. The choice to medicate should depend on what is best for the child and family preferences, with particular consideration given to the benefits of going on medication against the potential risks associated with medication side effects."

Stephanie D'Souza.
Stephanie D'Souza. Photo credit: The AM Show

D'Souza said some "grow out of it", while for others the condition persists into adulthood.

"Mostly the inattentive symptoms rather than the hyperactivity." 

Despite the growing number of kids diagnosed with ADHD, it's been nearly two decades since the Ministry of Health last updated its treatment guidelines for the disorder - it doesn't even mention "all currently publicly funded medications in New Zealand, let alone internationally approved and recommended ADHD medications such as clonidine and guanfacine", and uses "outdated diagnostic criteria from the DSM-IV rather than the current DSM-V".

DSM, or the Diagnostic and Statistical Manual of Mental Disorders, is the "authoritative volume that defines and classifies mental disorders in order to improve diagnoses, treatment, and research" produced by the American Psychiatric Association. DSM-V came out in 2013, and IV in 1994. 

"Any updated New Zealand guidelines should also consider the ethnic and socioeconomic disparities apparent in ADHD medication use, and take these into account in their recommendations so that equitable health outcomes can be achieved," the study concludes.