UK Autism Diagnosis over 20 Years


Full paper:


Nothing about us without us
Who: Russell and colleagues
Journal: The Journal of Child Psychology and Psychiatry
Published: 2021
Title: Time trends in autism diagnosis over 20 years: a UK
population-based cohort study

UK Autism Diagnoses Over 20 Years

This study wanted to look at how many new autism diagnoses there have been between 1998-2018. It seems to be the first study to look at diagnosis trends across developmental stages.


A number of studies have shown that while autism diagnoses appear to be increasing, that autism characteristics are remaining stable. This suggests not that there are more autistic people, but that more autistic people are being diagnosed.

Over the years, there has been a massive increase in adult diagnostic services. In 2009, 50% of local authorities had adult diagnostic services, and by 2019 93% of local authorities did. This was due to the Autism Act of 2009.

There has also been a push for the identification of autistic females in recent years, so this will be interesting to look into as well.


In the UK, over 98% of people are registered with a GP. GPs code data into a datalink called the Clinical Practice Research Datalink (CPRD).

The CPRD Aurum is a database which contains data from about 10% of GPs in England and Northern Ireland, and this data was utilised for this study. This data records self-reported gender (M/F) rather than sex.


Between 1998 and 2018, there was a 787% increase in autism diagnosis.

[A line graph shows an increase in autism diagnosis]


There was an increase in the average age of diagnosis, from 9.6yrs to 14.5yrs.

[A line graph shows an increase in autism diagnosis across different age groups; the largest increase is in 19+ years, then 6-11 years, then 12-19 years, and the least increase in 0-5 years.]


And there was also an increase in the number of females diagnosed.

[A line graph shows a larger increase in female diagnoses over male diagnoses]


The data did not seem to show an increase in autism characteristics, but an increase in diagnosis. This is shown by the fact that the same number of children aged 8 were diagnosed between 2005-2009. There were increased diagnoses in other age groups, which were previously missed.


There have been more autism diagnoses in adults and females over the years. This might be due to an increase in demand from the public for greater awareness of autistic people of different groups and the work by advocacy groups on de-stigmatization.

However, there is likely missing data from this study as people move towards private assessment due to NHS wait times.

It is important to note that an increase in autism diagnosis does not necessarily mean there is an increase in autistic people (although this cannot be ruled out), but that autistic people are now more readily identified and diagnosed.


Key points
-Previous UK studies have conflicting findings as to whether rates of autism diagnosis are increasing.
-Ours is first study to analyze the time trend of autism diagnosis in a population-based UK clinical cohort by developmental stage, level of severity and by gender, over a twenty-year period.
-Results show an exponential increase in use of autism diagnosis over time.
-New subpopulations previously seldom considered for autism diagnosis (females, adults) have steepest growth in diagnosis rates.
-Differing rates of increase between subgroups suggest effects are primarily due to increased recognition, although an actual increase in autism incidence cannot be ruled out.
-2009 UK policy to invest in adult assessment centers may underpin rise in adult diagnosis.
-Rising age at diagnosis in infancy and childhood suggests policy to improve early recognition of autism has had limited effect

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