Study Finds Rising ADHD and Autism Diagnoses Reflect Broader Identification, Not Just Increased Prevalence

A new study led by the Barcelona Institute for Global Health (ISGlobal) and Aarhus University indicates that the demographic profile of children and teenagers diagnosed with attention deficit/hyperactivity disorder (ADHD) or autism spectrum disorder (ASD) has shifted significantly over the last decade. Published in JAMA Psychiatry, the research suggests that the surge in diagnoses may be partly driven by who is being identified, rather than solely by changes in the underlying likelihood of developing these conditions.

Previous research has established that certain characteristics are more prevalent among individuals diagnosed with ADHD or ASD compared to the general population. These traits include premature birth, low birth weight, lower household income, less educated parents, a family history of psychiatric disorders, and higher prior utilization of healthcare services. The researchers sought to determine if these patterns persisted as diagnosis rates climbed.

To investigate, the team analyzed data from more than 2.1 million children and adolescents in Denmark. They compared over 71,000 young people diagnosed with ADHD or ASD between 2012 and 2022 against a control group of more than 713,000 individuals without such diagnoses.

The analysis revealed that while disparities remained, they steadily narrowed over the ten-year period. For instance, at the start of the study, children with low birth weight were 54% more likely to receive an ADHD or ASD diagnosis than those born at a normal weight. By the end of the study, that likelihood gap had shrunk to 17%. Similar declines were observed regarding premature birth and various measures of socioeconomic disadvantage.

Magnus Elias Tarp, a PhD student at Aarhus University and the study’s first author, emphasized that the results do not diminish the importance of risk factors. Instead, they highlight that recently diagnosed individuals bear a closer resemblance to the general population than those diagnosed ten years prior.

The findings suggest several potential drivers for this shift, including heightened awareness of neurodevelopmental conditions, improved identification by healthcare and education systems, expanded access to diagnostic evaluations, and evolving clinical thresholds for what constitutes impairing symptoms. However, the study could not quantify the specific contribution of each factor.

Oleguer Plana-Ripoll, a researcher at both ISGlobal and Aarhus University and the study’s senior author, noted that rising diagnosis rates should not be automatically interpreted as evidence that the actual occurrence of ADHD or ASD has increased proportionally. He clarified that the data does not imply overdiagnosis or reduced severity, but rather a change in the diagnosed population.

The researchers suggest these insights could reshape how scientists interpret prevalence trends and outcome reports. Apparent improvements in prognosis may partly stem from changes in the characteristics of those receiving diagnoses, rather than genuine advances in treatment. The authors also stressed the need for further research in other countries to verify whether these trends can be replicated globally.