Researchers have called for better support for people with attention deficit hyperactivity disorder (ADHD), after a review found hundreds of thousands could be undiagnosed.
Despite recent increases in diagnosis, UK researchers say the number of people with a recorded diagnosis of ADHD is still far below international estimates.
The gap was especially large for older adults, with just 0.05 per cent of adults over the age of 65 diagnosed with ADHD, which suggests more than 90 per cent of cases in this age group may be undiagnosed.
Greater awareness of ADHD and improved assessments mean it’s more often picked up in childhood today.
But in past decades, people with ADHD – especially women – were often forced to navigate life without the support a diagnosis can unlock.
Rates of new ADHD diagnosis increased significantly after 2020 in most age groups as understanding about the condition became more mainstream – and previous theories that women were not typically affected were disproven.
The researchers – from King’s College London, University College London and the University of Liverpool – say the findings show recorded diagnosis of ADHD are still unacceptably lower than the best available estimates.
‘Our findings highlight that ADHD is likely underdiagnosed across the lifespan,’ Dr Gavin Stewart, the study’s lead author, said.
Older adults with ADHD need more help after years of misdiagnosis, review finds
‘In recent years, there has been growing awareness of how neurodivergence has been overlooked in middle-aged and older people.
‘These ADHD findings mirror what we see in other types of neurodivergence, such as autism, where upwards of 90 per cent of middle-aged and older people are likely to not be formally recognised as being autistic.’
He added that a timely diagnosis often acts as a ‘gatekeeper’ to support – which may be crucial as people age.
‘The low rates observed in older adults don’t necessarily mean that ADHD is uncommon in older age.
‘Instead they may reflect historical differences in recognition and access to diagnosis, particularly among generations who grew up before ADHD was widely recognised.’
He added: ‘The majority of ageing neurodivergent people will not have received a diagnosis and be unsupported, which needs to be urgently addressed.’
The study – funded by the Medical Research Foundation and the British Academy – used anonymised data from more than 3.5 million people registered with GP practices in England in 2025 to estimate how many people had a diagnosis at this time.
They then compared this with published estimates of ADHD prevalence in the general population, from international studies using data from more than 42 million patients in England to examine trends over a 24-year period.
While global autism and ADHD rates have risen in recent decades, the trend is largely attributed to a better understanding and broadening definition of the neurodevelopmental conditions, rather than a genuine increase in the percentage of people affected.
The researchers also commented on how neurodiverse individuals fare – especially those who don’t receive a timely diagnosis – in life compared to neurotypical people.
‘ADHD can profoundly affect many aspects of a person’s life – education, work, relationships – and it often co-exists with other neurodevelopmental conditions,’ Dr Angela Hind, chief executive of the Medical Research Foundation, said.
A previous UCL-led study that compared 30,029 adults across the UK with diagnosed ADHD and 300,390 participants without ADHD found that adults with ADHD have reduced life expectancies.
‘When it goes undiagnosed or unsupported, people may spend years not understanding the challenges they face,’ Dr Hind continued.
‘We’re proud to support research that will help strengthen ADHD services and ensure more children and adults can get the recognition and help they need.’
Official data published by NHS England, using figures from the National Institute for Health and Care Excellence (NICE), found that as many as 2,498,000 people could be living with ADHD, including those not yet formally diagnosed.
At the same time, recent figures for autism assessments in England show the number of patients waiting at least three months for an initial specialist appointment has jumped by more than a quarter.
Experts warn that behind these numbers are a growing number of middle-aged and older adults unable to access vital support.
It comes as the proportion of people in the UK on ADHD medication has tripled in the past decade, with a 20-fold increase among young women.
Experts say the figures reflect growing recognition of the attention-deficit disorder as a lifelong condition and highlights the need for healthcare systems to plan for rising demand – with the NHS already overspending its budget for ADHD by £164m.
