Profile of people diagnosed with ADHD and autism has shifted over a decade, study finds

A study led by the Barcelona Institute for Global Health (ISGlobal) and Aarhus University has found that children and adolescents diagnosed with attention-deficit/hyperactivity disorder (ADHD) or autism spectrum disorder (ASD) in Denmark today resemble the general population more closely than those diagnosed a decade ago. Published in JAMA Psychiatry, the study suggests the rise in diagnoses may partly reflect changes in who is diagnosed.

Researchers analyzed data from more than 2.1 million children and adolescents in Denmark, comparing over 71,000 people diagnosed with ADHD or ASD between 2012 and 2022 with more than 713,000 peers without these diagnoses. Earlier studies have linked such diagnoses to factors including preterm birth, low birth weight, lower parental education or income, a parental history of psychiatric disorders, and greater health care use before diagnosis.

Diagnosed children and adolescents were still more likely than their peers to have these characteristics, but the gap narrowed steadily over the decade. Ten years ago, children born with low birth weight were 54% more likely to later receive an ADHD or ASD diagnosis than those born at a normal weight; by the end of the study period, that figure had fallen to 17%. Similar reductions appeared for preterm birth and socioeconomic disadvantage.

Magnus Elias Tarp, a doctoral student at Aarhus University and the study's first author, said the risk factors have not become unimportant — rather, "people diagnosed in recent years resemble the general population more closely than those diagnosed a decade ago." Senior author Oleguer Plana-Ripoll said the findings "do not show that these conditions are being overdiagnosed or that they have become less severe," but that the diagnosed population itself has changed over time.

The researchers say this matters for interpreting trends and planning health care, educational and social services, and note that some improvements reported in recent studies on outcomes for people with ADHD or ASD may partly reflect this changing profile rather than better prognosis.