Everyone has an opinion on why so many people are being diagnosed with ADHD and autism. Screens. Food. Schools. TikTok. "It did not exist in my day." What almost nobody has is data that can separate the explanations. A study published in JAMA Psychiatry in June 2026 has some, and it comes from an unusual place: the DNA of the people who were diagnosed.
What the Researchers Did
Denmark keeps a blood spot from almost every newborn, and national health registries record every diagnosis. The iPSYCH project links the two. Sonja LaBianca, Andrew Schork and their colleagues at the University of Copenhagen used it to study 37,000 people: about 17,000 diagnosed with autism and 20,000 with ADHD, all born between 1981 and 2008 and diagnosed between 1994 and 2016.
For each person they computed a polygenic score: the sum of thousands of small genetic variants that, together, nudge the odds of ADHD or autism up or down. No single variant matters. The total is a rough gauge of how much inherited liability someone carries. Then they asked a simple question: does the average score of diagnosed people depend on the year they were diagnosed?
What They Found
Over the period, diagnostic rates more than quadrupled. In Denmark, about 0.1% of the population had an ADHD diagnosis in 2000; by 2022 it was over 3%. And as the numbers rose, the average genetic load of newly diagnosed people fell: by roughly 10 to 15% for ADHD, by up to 25% for autism, around 20% on average. "We found a clear decline over time for both ADHD and autism diagnoses," LaBianca said.
The genetic profile itself did not change. The same variants mattered in 1996 and in 2016. What changed is how much of that liability a person needed to carry, on average, to end up with a diagnosis.
What It Means: The Bar Moved
Think of a height requirement. If "tall" means over 1.90 m, few people qualify, and they are all very tall. Lower the bar to 1.80 m and many more qualify, and the average height of the "tall" group drops, although nobody became shorter and the biology of height did not change. That is the pattern in the data. Schork calls it a "shifting diagnostic threshold".
If something in the environment were creating new cases out of nothing, screens or diet or anything else, you would not expect this signature. The most economical reading is that diagnosis now reaches people it used to miss: girls and women, adults, people without intellectual disability, people whose difficulties are real but less visible. We wrote about that group in late diagnosis in women and in ADHD signs in women. The researchers list the likely drivers themselves: revised diagnostic manuals, less stigma, more help-seeking, and the arrival of treatment for adult ADHD.
What It Does Not Mean
It does not mean recent diagnoses are fake. LaBianca is explicit: "Our results do not invalidate people's diagnosis of ADHD or autism. Rather, they show that clinical practice, diagnostic manuals and society's understanding of these diagnoses have changed to be broader over time." A diagnosis is made on symptoms and impairment, not on DNA, and a person with an average polygenic score can struggle as much as one with a high score.
It does not prove overdiagnosis either. A lower bar can mean over-inclusion, or it can mean the old bar was too high and left people without help for decades. Genetics cannot tell those apart; only outcomes can. And polygenic scores capture a small part of the inherited risk. Twin studies put heritability around 0.76 for ADHD, as we explain in ADHD genes beyond dopamine, while today's scores explain a few percent.
Three limits are worth keeping in mind. The data stop in 2016, before the post-pandemic surge in adult diagnoses. They come from one country with one health system. And the participants are overwhelmingly of European ancestry.
If You Are Wondering About Yourself
The practical message is reassuring. ADHD and autism did not appear from nowhere; they have always been there. What changed is who gets noticed. If you recognise yourself in the descriptions and were never assessed, you are exactly the kind of person the older, higher bar used to miss.
A validated screener is a sensible first step. The ASRS-v1.1 for ADHD and the AQ-10 for autism take a few minutes, are free here, and give you a score you can bring to a professional. If both seem to fit, that is common too: see when autism and ADHD overlap.
Source: LaBianca S, Schork AJ, et al. Changes in genetic contributions to ASD and ADHD by year of diagnosis. JAMA Psychiatry, June 10, 2026. DOI 10.1001/jamapsychiatry.2026.1450. Figures and quotations are from the article and from the University of Copenhagen and Lundbeck Foundation releases; the explanations in plain language are ours. This article is educational and is not a diagnosis.