Shifting Profiles of ADHD and Autism Diagnoses Explained by Major Study

Recent scientific research indicates that the demographic and clinical profile of children and adolescents diagnosed with attention deficit/hyperactivity disorder (ADHD) or autism spectrum disorder (ASD) has undergone significant shifts over the last ten years.

Conducted by the Barcelona Institute for Global Health (ISGlobal)—a center supported by the “la Caixa” Foundation—and Aarhus University, the study reveals that individuals diagnosed with ADHD or ASD in Denmark today bear a closer resemblance to the general population than those diagnosed a decade ago.

These findings suggest that the rising rates of ADHD and ASD diagnoses may partly reflect shifts in diagnostic practices and identification criteria, rather than solely indicating a genuine increase in the underlying prevalence of these conditions. The research was published in JAMA Psychiatry.

Tracking Changes in ADHD and Autism Diagnoses

Earlier research has highlighted several factors that are more common among individuals diagnosed with ADHD or ASD compared to the general population. These include premature birth or low birth weight, parental educational or socioeconomic disadvantages, a family history of psychiatric disorders, and higher utilization of healthcare services prior to diagnosis.

Investigators sought to determine whether these associated patterns have evolved as ADHD and ASD diagnoses have become increasingly prevalent.

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

Differences Narrowed Over 10 Years

While young individuals diagnosed with ADHD or ASD remained more likely than their peers to exhibit many of the previously identified risk factors, the magnitude of these disparities decreased steadily over the ten-year study period.

Low birth weight serves as a key example. At the start of the study period, children born with low birth weight were 54% more likely to receive an ADHD or ASD diagnosis later in life compared to those born at a normal weight. By the conclusion of the study, this disparity had narrowed to just 17%.

Researchers observed similar declines in the correlations between premature birth, various indicators of socioeconomic disadvantage, and these diagnoses.

“The key message is not that these risk factors are no longer important,” explains Magnus Elias Tarp, a PhD student at Aarhus University and the study’s lead author. “What we have found is that individuals diagnosed in recent years resemble the general population much more closely than those who received the same diagnoses a decade ago.”

A Different Way to Understand Rising Diagnoses

Much of the existing literature has focused on why ADHD and ASD diagnosis rates are rising or identifying risk factors associated with these conditions. This new study takes a different approach by investigating whether the actual population receiving diagnoses has changed over time.

The researchers suggest that several societal and systemic factors could contribute to this shifting landscape. Increased public awareness, more effective identification by healthcare and education systems, expanded access to diagnostic evaluations, and evolving clinical thresholds for what constitutes an impairing neurodevelopmental trait may all play a role.

While the study cannot quantify the individual contribution of each factor, the findings suggest that rising diagnosis rates should not be automatically equated with a proportional 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, a researcher at ISGlobal and Aarhus University, and the study’s senior author. “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.

What the Findings Could Mean

Experts note that these results could influence how scientists interpret prevalence trends for ADHD and ASD. Additionally, the findings may be highly valuable for shaping healthcare, education, and social support services tailored to individuals with these diagnoses.

Furthermore, the findings could impact how researchers interpret reports of improving outcomes for individuals with ADHD or ASD. Some apparent progress may stem partly from changes in the characteristics of the newly diagnosed population, rather than representing a genuine improvement in the prognosis of the conditions themselves.

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