New research suggests that the characteristics of children and teenagers receiving attention deficit/hyperactivity disorder (ADHD) or autism spectrum disorder (ASD) diagnoses have shifted over the past decade. The study, led by the Barcelona Institute for Global Health (ISGlobal), a centre supported by the "la Caixa" Foundation, and Aarhus University, found that young people diagnosed with ADHD or ASD in Denmark now more closely resemble the broader population than those who received the same diagnoses 10 years earlier. The findings suggest that the increase in ADHD and ASD diagnoses may partly reflect changes in who is being identified and diagnosed, alongside any possible changes in the underlying likelihood of developing these conditions.
The research was published in JAMA Psychiatry. Tracking changes in ADHD and autism diagnoses Previous studies have identified several characteristics that occur more often among people diagnosed with ADHD or ASD than among the general population. These include being born prematurely or at a low birth weight, having parents with lower levels of education or lower household income, having a parent with a history of psychiatric disorders, and making greater use of healthcare services before receiving a diagnosis.
Researchers wanted to know whether those patterns had changed as ADHD and ASD diagnoses became more common. To investigate, the team analyzed information from more than 2.1 million children and adolescents in Denmark. The researchers compared more than 71,000 young people diagnosed with ADHD or ASD between 2012 and 2022 with more than 713,000 individuals who had not received either diagnosis.
Young people diagnosed with ADHD or ASD were still more likely than their peers to have many of the characteristics previously linked with these conditions. However, the size of those differences steadily declined during the study period. Low birth weight provides one example.
At the beginning of the study period, children born with low birth weight were 54% more likely to later receive an ADHD or ASD diagnosis than children born at a normal weight. By the end of the study, the difference had dropped to 17%. Researchers found comparable declines in the associations involving premature birth and several measures of socioeconomic disadvantage.
"The key message is not that these risk factors are no longer important," says Magnus Elias Tarp, PhD student at Aarhus University and first author of the study. "What we found is that people diagnosed in recent years resemble the general population more closely than those who received the same diagnoses a decade ago." A different way to understand rising diagnoses Much of the research surrounding ADHD and ASD has examined why diagnosis rates are increasing or which factors are associated with a greater likelihood of developing these conditions. The new study approaches the trend from another direction by asking whether the population receiving diagnoses has itself changed.
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