The medical profiles of adults diagnosed with autism have changed hugely since 2010, finds a study of medical records in the UK and Sweden, published in the online journal BMJ Mental Health.
There's been a pronounced shift from a prior diagnosis of epilepsy, psychosis and intellectual disability to ADHD (attention deficit hyperactivity disorder), anxiety, and depression since 2010, the data analysis indicates.
And the steepest rise in diagnoses has been among 16-20 year olds, females, and those of White ethnic background.
The number of people being diagnosed with autism has increased worldwide in recent
decades, although it's not entirely clear if this has been driven by greater public awareness, reduced stigma, or changes in diagnostic practice, say the researchers.
To explore this further, the researchers studied UK primary care records up to 2023 ( CPRD
Aurum ; 47,413,279 patients from 1784 general practices) and Swedish population-wide registry data (13,345,950 people) up to 2021 to look at trends over time.
They particularly wanted to find out if the social and demographic patterns of incident and prevalent autism diagnoses in adults, and the prevalence of other concurrent neuropsychiatric conditions, have changed over time. They also wanted to know if these trends are consistent in direction and magnitude across both the UK and Sweden.
Eligibility criteria included study entry on 1 January 2010, 16 years of age and, in the UK, at least 1 year registered at a general practice. Monitoring ended at death, ceasing to be registered at a general practice (UK), emigration (Sweden), or study end date (31 December 2023 in the UK and 31 December 2021 in Sweden), whichever came first.
The data were analysed for each person's first recorded diagnosis of: autism; intellectual disability; ADHD; epilepsy; migraines/headaches; anxiety; depression; psychosis; bipolar disorders; obsessive-compulsive disorder and related conditions; stress-related conditions (including post-traumatic stress disorder); eating disorders; personality disorders; suicidality/self-harm; sleep disorders; and chronic fatigue.
First recorded prescriptions (UK) or dispensations (Sweden) of antipsychotics; antidepressants; antiseizure medications; opioids; gabapentinoids; melatonin and benzodiazepines/z-drugs (sedatives) were also noted.
In the UK, 24,537,039 adults contributed to the study, 141,119 of whom had been diagnosed with autism. In Sweden, 9,096,874 adults contributed, 100, 817 of whom had been diagnosed with autism.
Incident (first recorded) autism diagnoses in adults were consistently higher in Sweden than in the UK, but the number of new cases rose sharply in the UK after 2020.
In the UK, rates of new diagnoses increased from 6/100,000 people in 2010 to 64 in 2023. In Sweden, they rose from 43/100,000 people in 2010 to 65 in 2021.
New diagnoses increased fastest for 16–20 year-olds in both nations, rising from
31/100,000 people in 2010 in the UK to 364 in 2023, and from 165/100,000 people in 2010 in Sweden to 361 in 2021.
New diagnoses also rose fastest in females in both nations, as well as in people of White ethnicity in the UK and those with Swedish-born parents in Sweden.
In both countries, age-standardised prevalence was consistently higher for males than females, increasing in both sexes over the study period to 1.4% for males and 0.7% for females in the UK in 2023, and to 1.8% for males and 1.2% for females in Sweden in 2021.
Prevalence also increased over time in all age groups and was consistently higher in younger age groups. The prevalence of autism among 16–20 year-olds was 4.1% in 2023 in the UK and in Sweden in 2021.
Over time, the proportion of adults with autism who had a prior diagnosis of epilepsy, psychosis, and/or intellectual disability fell while the proportion of those with a prior diagnosis of ADHD, anxiety, depression, and other mental illnesses increased.
For example, in the UK between 2010 and 2023, a history of epilepsy among adults with newly diagnosed with autism fell from 10% to 4%, while a history of anxiety rose from 29% to
just over 58%. Trends were broadly consistent between both sexes.
This is an observational study, and as such, can't establish the reasons for the observed changes in the profiles of those diagnosed with autism.
But point out the researchers: "The characteristics of individuals diagnosed as autistic have changed dramatically since 2010 in both the UK and Sweden."
And they conclude: "While these data are unable to shed light on whether these changes indicate greater appreciation of nuanced forms of autism, or misdiagnoses of other psychiatric presentations as autism, efforts will need to be made to recognise and address the needs with appropriate support."
