Your quote doesn’t say they calculate the result globally. It’s estimated based on the results in Carolina. They say estimate because the don’t have the data to say it is true.
ADHD administrative prevalence (based on rates of diagnosis and/or prescriptions) in children and adolescents in the UK has been estimated to fall between 0.2 and 0.9% since the mid-2000s (39). These rates remain below community prevalence estimates in the UK estimated at around 2.2% in 1999 and 2005 (55, 56), with more recent estimates of 1.6% in 2017, based on the more restrictive ICD-10 Hyperkinetic Disorder criteria (57). Administrative prevalence of adult ADHD in the UK stands at around 0.1% (40), far below even some of the lowest prevalence rates documented in adults (9).
- Failure of Healthcare Provision for Attention-Deficit/Hyperactivity Disorder in the United Kingdom: A Consensus Statement, 2021
This suggests about 1% of the UK population has ADHD and isn’t diagnosed. The would be more than 600,000 people.
This is a little misleading. Like most macro trends, the actual situation is far more complicated. Here’s a study describing under diagnosis of ADHD in adults
While it’s likely true that the condition is overdiagnosed in adolescent populations, it’s also widely acknowledged that ADHD is less commonly diagnosed once in adulthood.
Unfortunately, that study was done a couple of hundred years after the UK lost control of North Carolina, so it doesn’t support the claim that ADHD medication is overprescribed in the UK.
