Why is it that kids and teens who are diagnosed these days with autism or ADHD have more in common with the mainstream than they did 10 years ago?
This is the conclusion of a study from the Barcelona Institute for Global Health and Aarhus University.
The findings were published in JAMA Psychiatry.
Researchers have known that certain characteristics are more common among people diagnosed with ADHD or autism when compared to the general population.
These include premature birth, low birth weight, socioeconomic disadvantage, having a parent with a psychiatric history and greater use of healthcare services before diagnosis.
The study asked whether those patterns have changed as diagnosis rates have risen.
The researchers examined records from more than 2.1 million kids and adolescents in Denmark.
They compared more than 71,000 young people diagnosed with ADHD or autism between 2012 and 2022 with more than 713,000 who had neither diagnosis.
The diagnosed group continued to show many characteristics associated with ADHD and autism.
But the differences between diagnosed young people and their peers became progressively smaller.
Low birth weight is one example.
Early in the study period, babies with low birth weight were 54% more likely to eventually receive an ADHD or autism diagnosis than those born at normal weight.
By the end of the period, that difference had fallen to 17%.
Similar changes were found for premature birth and several measures of socioeconomic disadvantage.
The researchers stressed that these factors have not stopped being relevant.
Instead, people receiving diagnoses in recent years more closely resemble the wider population in these respects.
Why ADHD and Autism Diagnoses Are Increasing
You may be thinking that this is due to increased awareness and narrative, particularly on Instagram and TikTok.
Or, you may be supposing that it’s due to the easy access to online “autism tests” or ADHD checklists — for which results could prompt people to seek an assessment.
Many autistic people blog about their lived experiences, and this can resonate with individuals who’ve always felt different and struggled socially — prompting them to get an evaluation.
These explanations ring very valid for the increased rate of diagnoses for both ASD and ADHD.
In addition, healthcare and school systems may also be better at recognizing these conditions, while more diagnostic clinics have popped up.
There may also have been changes in how much neurodevelopmental difficulty is considered significant enough to warrant a diagnosis.
What the Study Does Not Show
Do not confuse an increase in diagnoses with an increase in the actual conditions.
It’s quite possible, and in fact, strongly believed in the autism community, that decades ago, throngs of autistic people got to adulthood and lived a long life without ever having been diagnosed.
That’s happening less these days, due to the aforementioned reasons.
But the study’s findings do not establish that autism, or ADHD, themselves have become more common or less severe.
The Denmark study explains that rising diagnosis rates can’t automatically be taken as evidence that the occurrence itself of these conditions has increased by the same amount.
The researchers also say the study does not demonstrate that ADHD or autism are being overdiagnosed.
Though some conditions can strongly mimic ADHD, such as untreated sleep apnea, there really aren’t any conditions that strongly mimic autism in terms of multiple traits at once.
For example, sensory processing disorder can mimic the sensory issues of autism — but only the sensory issues.
Social anxiety disorder can mimic the difficulties in social settings common in autism — but only the difficulties in social settings.
Whereas, untreated sleep apnea mimics numerous traits of ADHD: trouble with concentration and focus, deficits with attention and staying on task, being short tempered, fidgety and moody.
There is no single disorder that can mimic numerous classic traits of autism.
So while I had previously suspected ADHD in myself due to a very high propensity to daydream, ADHD flopped at explaining my high propensity to get fixated on odd topics, to relentlessly overthink, to rehearse anticipated conversations and replay on loop past conversations, peculiar stimming behaviors (repetitive movements), preference for solitude, extreme attention to detail, rigid thinking, feeling disconnected from humans all my life — need I go on?
The paper points out that more research in other countries will be needed to determine whether the same pattern appears outside Denmark.
