New research reveals that children diagnosed with ADHD and autism now resemble the general population more closely than a decade ago, suggesting expanded diagnostic criteria.
By Adam Makins·
A sweeping study of over 2 million Danish children and adolescents challenges how we interpret the dramatic rise in ADHD and autism spectrum disorder diagnoses. Rather than indicating these conditions have become more common, the research suggests something more nuanced is happening: the population receiving diagnoses has fundamentally changed.
The study, published in JAMA Psychiatry and led by researchers at Barcelona Institute for Global Health and Aarhus University, compared children diagnosed with ADHD or ASD between 2012 and 2022 against those without diagnoses. What they discovered upends a common assumption about rising diagnosis rates.
Consider low birth weight, a characteristic long associated with higher ADHD and ASD risk. A decade ago, children born with low birth weight were 54% more likely to receive these diagnoses than normal-weight peers. By 2022, that gap had shrunk to just 17%. Similar patterns emerged across other historical markers: premature birth, parental education levels, household income, and parental psychiatric history all showed declining associations with diagnosis.
This doesn’t mean these risk factors disappeared. They didn’t. What changed is who gets diagnosed. Young people receiving ADHD and ASD diagnoses in recent years increasingly resemble the broader population, suggesting diagnostic nets have widened considerably.
The implications are substantial. Rising diagnosis rates shouldn’t automatically trigger alarm about overdiagnosis or underdiagnosis. Instead, they reflect a genuine shift in diagnostic practice. Multiple factors likely contributed: increased awareness among parents and educators, improved identification systems within schools and healthcare, expanded access to evaluations, and potentially changing thresholds for what constitutes clinically significant impairment.
Magnus Elias Tarp, the study’s first author, emphasizes the careful distinction researchers are making. “The key message is not that these risk factors are no longer important,” he explains. The finding is simply that diagnosis patterns have evolved.
This discovery carries real weight for how we plan services. Schools and healthcare systems that anticipate patient populations based on outdated demographic assumptions may misallocate resources. A generation ago, ADHD diagnoses clustered among disadvantaged children. Today’s diagnosed population is more demographically diverse, which could mean either better access for underserved groups or simply different patterns of who seeks and receives care.
Perhaps most intriguingly, these findings reshape how we should interpret reported improvements in outcomes for people with ADHD and autism. When studies show better functioning or improved symptoms over time, we’ve typically credited advances in treatment or understanding. But some of that apparent improvement might simply reflect that the baseline population has changed. If recent diagnoses include people with milder presentations, average outcomes would naturally look better.
Oleguer Plana-Ripoll, senior author, carefully avoids claiming these conditions are being overdiagnosed. The research doesn’t support that conclusion. Instead, it shows that “the population receiving these diagnoses has changed over time, and this needs to be taken into account when interpreting current trends.”
The researchers appropriately acknowledge their limitation: they can’t determine exactly which factors drove the shift or by how much. Danish data may also differ from other countries. The findings demand replication across different healthcare systems and cultures before we draw universal conclusions.
Yet the core insight feels robust and important. Diagnosis rates reflect both true disease prevalence and who gets identified and labeled. Understanding this distinction matters enormously for everyone from policymakers allocating resources to parents wondering whether their child should seek evaluation. When your neighbor’s kid gets diagnosed with ADHD in 2024, it means something different than the same diagnosis would have meant in 2014, not necessarily because the condition itself has changed, but because the criteria, awareness, and pathways to diagnosis have transformed so dramatically.
Source: Barcelona Institute for Global Health (ISGlobal)
