The true number of autistic people could be twice as many as previously thought, when the number of adults with undiagnosed autism are included in estimates.
The government estimates that around 700,000 people in the UK are autistic, but new research published in The Lancet Regional Health Europe estimates the number could be closer to 1.2 million.
Using data from GP practices in England between 2000 and 2018, the researchers calculated the number of people who had received an autism diagnosis and then compared these figures to a lower and upper estimate of how common autism really is in the population.
Lower estimates predict that around 1% of the population are autistic. This figure came from epidemiological research published in 2011, before changes to the diagnostic criteria for autism that made them more inclusive.
The upper estimate of 3% is based on rates of diagnosed autism in people aged 10 to 19. The researchers felt this figure was important to include because young people are most likely to have had their autism recognised since providers are now very aware of autism in young people.
The research therefore provides broad estimates, that mean between 150,000 and 500,000 people aged 20 to 49 years-old may be autistic but undiagnosed, while around 250,000 and 600,000 people over the age of 50 may be autistic and undiagnosed – more than 9 in 10 of all autistic people.
By calculating the mean average of these estimates, the researchers suggest there could be around 750,000 undiagnosed autistic people aged 20 and above in England, bringing the total number of autistic people to over 1.2 million.
The authors of the study are now calling for better access to diagnostic services for adults so that autistic people can get the help and support they need.
Lead researcher, Elizabeth O’Nions (UCL Psychology & Language Sciences), said: “Historically, autism has been considered as a condition of childhood. But recently, awareness has been growing that it is present across the lifespan – in adults as well as young people.
“Nevertheless, autism is still under-recognised in adults. Our estimates suggest that about 180,000 people aged 20-plus had an autism diagnosis as of 2018, meaning that most autistic adults in England were undiagnosed.”
O’Nions said receiving a diagnosis is important for autistic people because they may have unmet support needs, and it is much harder to receive this support without a diagnosis.
“Having a diagnosis means that someone can advocate for their right to reasonable adjustments and the support they need. Recognising that someone with an intellectual disability is autistic can also help people to understand and support them better,” she said.
O’Nions is also calling for greater acceptance and understanding of neurodiversity in society, as the research suggests that currently, there is an extreme lack of this recognition in society, particularly among healthcare professionals.
“Our findings indicate that there is still a substantial diagnostic gap in adults compared to children and young people when it comes to autism in England.
“This may partly reflect a lack of awareness and understanding of autism in adults on the part of healthcare professionals. Older adults may also be less likely to self-identify as autistic, meaning that they do not come to the attention of services.
“Meanwhile, providers may be hesitant to raise the issue of autism given the uncertainty around waiting times for a diagnosis and the availability of support or specialist services post-diagnosis,” she said.
