Study suggests the profile of people diagnosed with ADHD and autism has changed over the past decade

A study led by the Barcelona Institute for Global Health (ISGlobal), a centre supported by the ”la Caixa” Foundation, and Aarhus University shows that children and adolescents diagnosed with attention-deficit/hyperactivity disorder (ADHD) or autism spectrum disorder (ASD) in Denmark today share more characteristics with their peers in the general population than those diagnosed a decade ago. The findings suggest that the rise in diagnoses observed over the past decade may reflect, at least in part, changes in the characteristics of the people receiving these diagnoses, in addition to possible changes in the underlying risk of developing these conditions. The study has been published in JAMA Psychiatry.

A changing profile of diagnosed individuals

For many years, research has shown that certain characteristics are more common among people diagnosed with ADHD or ASD than among the general population. These include pregnancy- and birth-related factors such as preterm birth and low birth weight; family and socioeconomic factors such as lower parental education or household income; a parental history of psychiatric disorders; and greater use of healthcare services before diagnosis.

To investigate whether the profile of diagnosed individuals has changed over time, the researchers analysed data from more than 2.1 million children and adolescents living in Denmark. They compared more than 71,000 individuals diagnosed with ADHD or ASD between 2012 and 2022 with more than 713,000 peers without these diagnoses.

The results show that, although children and adolescents diagnosed with ADHD or ASD were still more likely than their peers to present these characteristics, the differences became progressively smaller over the study period. For example, ten years ago, children born with low birth weight were 54% more likely to receive a subsequent diagnosis of ADHD or ASD than those born at a normal weight. By the end of the study period, that difference had fallen to 17%. Similar reductions were observed for preterm birth and several indicators 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 new perspective on the rise in diagnoses

Most research on ADHD and ASD has focused on why diagnoses are increasing or on identifying factors that increase the risk of developing these conditions. This study asks a different question: whether the characteristics of the people receiving these diagnoses have also changed over time.

The authors suggest that this shift may reflect several factors, including greater awareness of ADHD and ASD, improved identification by healthcare and educational services, broader access to diagnostic assessment, or changes in the threshold at which neurodevelopmental traits are considered clinically impairing. While the study cannot determine the relative contribution of each of these factors, it suggests that the increase in diagnoses should not be interpreted solely as evidence of an increase in the underlying occurrence of ADHD or ASD.

"Our findings help us better understand why ADHD and autism diagnoses have increased so markedly in recent years," says Oleguer Plana-Ripoll, researcher at ISGlobal and Aarhus University and senior author of the study. "They do not show that these conditions are being overdiagnosed or that they have become less severe. Rather, they indicate that the population receiving these diagnoses has changed over time, and this needs to be taken into account when interpreting current trends. Further research in other countries would be needed to determine whether these findings can be replicated elsewhere", he adds. 

Implications for research and service planning

According to the researchers, these findings have important implications for interpreting trends in the prevalence of ADHD and ASD and for planning healthcare, educational and social services.

The results also suggest that some of the improvements reported in recent studies on outcomes among people with ADHD or ASD may partly reflect changes in the profile of the diagnosed population rather than changes in the prognosis of these conditions themselves.

Reference:
Tarp ME, Lousdal ML, Rask CU, Keyes KM, Formánek T, Brikell I, Liu X, Maseras GT, Plana-Ripoll O. Changes in Characteristics Associated With ADHD and ASD Diagnoses in Denmark Over Time (2012–2022). JAMA Psychiatry. 2026. DOI:10.1001/jamapsychiatry.2026.2722