The threshold for a diagnosis of ADHD and autism has expanded so far that people with the conditions are virtually indistinguishable from those without, scientists have suggested.
Experts have found that the characteristics of people with the condition have changed dramatically over the past decade.
Established risk factors, such as congenital problems and low family income, have much less influence today.
Meanwhile, doctors are seeing a clear increase in ‘milder’ cases.
The number of ADHD diagnoses in Britain has increased approximately twenty-fold over the past two decades, with referrals to specialist appointments increasing by 20 percent in the past year alone.
Meanwhile, there are an estimated 700,000 autistic Britons. Research shows that the number of autism diagnoses in Britain increased by 787 percent between 1998 and 2018.
Experts have recently raised concerns about the rising incidence of developmental problems in Britain, with some accusing doctors of ‘medicalising normal behaviour’.
Last month, Professor Dame Uta Frith, a pioneer in autism research, said: ‘When [autism] It was first identified in the 1940s and affected a small group of children with severe problems in social interaction, communication and behaviour.
Danish scientists say children diagnosed in 2012 were much more likely to show features historically linked to the disorders than those in 2022
‘Over time the definition has been expanded to include people with milder characteristics and without language or learning difficulties.
“Today, anyone of any age or intelligence level can be diagnosed with autism if he or she meets certain criteria.”
The team behind the new study – led by Aarhus University in Denmark – said ‘traditional risk factors’ are becoming less common among people with a diagnosis.
They highlighted a ‘shift’ in the definition of ‘disorder’ with regard to various ‘neurodevelopmental features’.
“Miller traits are more likely to be associated with disability and diagnosis,” they wrote in the journal JAMA Psychiatry. ‘This could contribute to increasing the incidence.’
Scientists in the study analyzed approximately 71,300 Danish children diagnosed with autism and ADHD between 2012 and 2022.
During this period, the number of diagnoses rose from 4,944 to 9,179 – an increase of 86 percent.
They found that children born with a low birth weight in 2012 had a 54 percent higher chance of being diagnosed with autism or ADHD compared to children born with a normal weight.
However, by 2022 this had fallen to just 17 percent.
The link between family income and a diagnosis also shifted, specifically with ADHD.
At the start of the study, one in four diagnosed children had a poorly educated mother, but by 2022 this would have fallen to about one in seven.
In total, the researchers examined 19 characteristics before diagnosis. This included family income, whether parents lived together, parental health and age at birth, as well as use of general practitioners or psychologists before diagnosis.
The study authors say that over the past decade, those diagnosed with ADHD or autism “became more and more similar” to those without a diagnosis.
Autism and ADHD are often closely linked because they are both neurodevelopmental disorders, but they are different.
According to the NHS, autism affects the way people communicate, interact with others and experience the world around them.
Autistic people may also think and process information differently, preferring routines and being more sensitive to sights, sounds, smells or touches.
Meanwhile, ADHD, or attention deficit hyperactivity disorder, affects concentration, activity level and impulse control.
Symptoms may include being easily distracted or forgetful and having difficulty following instructions.
Authors of the new study emphasized that the findings should not be interpreted as evidence that ADHD or autism have become less disabling.
Commenting on the findings, Professor Frith, who was not involved in the research, confirmed that newly diagnosed individuals today “look much more like their unaffected peers.”
“The implication of this is that the proportion of mild cases increases and severely affected individuals become less visible,” she added.
