Autism and ADHD are on the rise due to widening diagnostic criteria
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- Sonja LaBianca at Copenhagen University Hospital led a study of 140,000 people in Denmark's iPSYCH cohort, including 37,000 diagnosed with ADHD or autism between 1994 and 2016, finding that recently diagnosed individuals had significantly lower polygenic risk scores than earlier cohorts.
- Researchers applied polygenic risk scores built from 2018–2019 genome-wide association studies and found that the broadening of diagnostic criteria — not people previously diagnosed with other conditions being reclassified as neurodivergent — best explains the rise, LaBianca said.
- Autism and ADHD diagnoses have risen up to tenfold globally over the past two decades, with the steepest increases among girls and adults, according to the study background.
- LaBianca's team tested three competing explanations: widened diagnostic thresholds, reclassification of prior mental health diagnoses as neurodivergence, and improved awareness finding people who previously fell through the gaps — with widened criteria emerging as the strongest fit.
- Even the lowest-scoring diagnosed individuals in the study carried significantly more ADHD- and autism-linked risk variants than neurotypical controls, a finding LaBianca said rules out overdiagnosis: 'I would [only] use that term if we were diagnosing individuals at the same polygenic level as the background population.'
- Tinca Polderman at Vrije University Amsterdam backed the broader-criteria explanation but cautioned that 'polygenic risk scores provide just a piece of the puzzle,' warning against treating genetics and environment as separate drivers.
- The study was published in JAMA Psychiatry (DOI: 10.1001/jamapsychiatry.2026.1450) and noted that better awareness and reduced stigma may also contribute, though the researchers said they have less data to support those factors.
Why it matters: The findings reframe a heated public debate: if polygenic scores show today's newly diagnosed ADHD and autism patients still carry genuine genetic risk, health systems and insurers cannot dismiss the surge as overdiagnosis — but they must reckon with where the diagnostic line is being drawn and whether the same broadening is masking environmental drivers that the genetic data cannot see.
