The diagnostic threshold for Attention Deficit Hyperactivity Disorder (ADHD) and autism has widened considerably, leading to a situation where individuals with these conditions are increasingly similar to those without, according to a recent study by Danish scientists. The characteristics observed in individuals diagnosed with ADHD and autism have changed significantly over the past decade, with traditional risk factors playing a less influential role.
Researchers from Aarhus University in Denmark analyzed data from approximately 71,300 Danish children diagnosed with autism and ADHD between 2012 and 2022. During this period, diagnoses rose by 86 percent, from 4,944 to 9,179. The study, published in JAMA Psychiatry, found a notable shift in the factors associated with these diagnoses. For instance, in 2012, children born with low birth weight had a 54 percent higher likelihood of receiving an autism or ADHD diagnosis compared to those born at a normal weight. By 2022, this figure had decreased to 17 percent.
The influence of family income on ADHD diagnoses also changed. At the beginning of the study period, one in four diagnosed children had mothers with lower educational attainment; by 2022, this proportion had fallen to approximately one in seven. The researchers examined 19 characteristics, including family income, parental cohabitation, parental health and age at birth, and prior use of healthcare services, finding that those diagnosed with ADHD or autism became more alike their unaffected peers over the decade.
Experts noted a distinct increase in milder cases being diagnosed. Professor Dame Uta Frith, a prominent autism researcher not involved in the study, commented that newly diagnosed individuals today appear more similar to their unaffected peers than in the past. She suggested this indicates a rise in the proportion of mild cases, making severely affected individuals less visible. This broadening of diagnostic criteria has led to concerns among some experts about the potential "medicalization of normal behavior."
ADHD and autism are both neurodevelopmental conditions, though they differ in their presentation. Autism affects social interaction, communication, and sensory experiences, while ADHD impacts concentration, activity levels, and impulse control. The study authors emphasized that their findings should not be interpreted as evidence that ADHD or autism have become less debilitating, but rather that the definition and identification of these conditions have evolved.