Danish Study Finds Recent ADHD and Autism Diagnoses Carry Lower Genetic Risk Scores

A study of 140,000 people from the iPSYCH cohort in Denmark found that those diagnosed with ADHD or autism more recently carried lower polygenic risk scores for the conditions than people diagnosed earlier. The analysis covered 37,000 individuals diagnosed between 1994 and 2016.

People diagnosed in later years also showed lower polygenic risk scores for other mental health conditions and for traits such as impulsivity.

Even those with the lowest scores still had more risk variants than the neurotypical control group. Researchers created the polygenic risk scores using genome-wide association studies published in 2018 and 2019. They tested three scenarios for the rise in diagnoses and identified broadening of diagnostic criteria as the strongest explanation.

Diagnoses of autism and ADHD have increased up to tenfold worldwide over the past two decades, with the largest gains among girls and adults. ADHD and autism are highly heritable, and thousands of common gene variants each contribute a small increase in likelihood of core traits.

Sonja LaBianca of Copenhagen University Hospital said the best explanation for rising cases is the broadening of diagnostic criteria.

She added that better awareness and reduced stigma may also play a role but that supporting data remain limited. Tinca Polderman of Vrije University Amsterdam said broadening of criteria is the most likely driver yet cautioned that polygenic risk scores capture only part of the picture. 2026.1450.