The 19 features above are either risk factors for ADHD and autism or are associated with the diagnoses. In most cases, their association with these diagnoses grew weaker since 2012, suggesting today’s patients look more like the normal population than those of days past.
Diagnosis rates have soared for both conditions: has the diagnosis itself changed?
STUDY: Tarp ME et al, JAMA Psychiatry 2026
STUDY TYPE: Population-based matched case-control study
FUNDING: Independent Research Fund Denmark and other public/nonprofit foundations (Denmark, Sweden)
Background
Diagnoses of ADHD and autism have risen sharply in recent decades. This study asked whether children diagnosed more recently differ from those diagnosed a decade earlier on well-established risk factors.
The Study
- 71,317 Danish children diagnosed with ADHD or autism between 2012 and 2022 (median age, 11.4 years), matched to 713,170 controls by sex, birth year, and residence.
- Compared 19 associated features of the disorders (eg, parental and family factors, perinatal complications, health care use) across five time periods.
- Measured whether odds ratios for these characteristics rose or fell over the decade.
Results
Patients diagnosed 15 years ago differed more from normal (neurotypical) people than those diagnosed in recent days. In other words, today’s ADHD and autism looks more like normality.
But not full normality. The 19 related features they looked at were still more common among diagnosed people than normals, even if the differences shrank over the years.
Here are some examples of specific markers. For low birth weight, the odds ratio fell from 1.54 in 2012-2013 to 1.17 in 2020-2022, about a 3% yearly decline. Low household income showed similar decrease, more for ADHD than autism (6.5% versus 0.7% yearly change) and more among adolescents than younger children. Parental psychiatric illness and doctor visits were exceptions, staying stable or strengthening.
The study only looks at a brief period, but covers the shift from DSM-IV to DSM-5 in 2013. A 2019 study found similar trends for autism, tracing back to the 1980s. As time went on, the autism cohort looked more like the neurotypicals on psychological testing.
Limitations
Registry diagnoses don’t include severity. Private-practice diagnoses may be undercounted, and findings may not generalize beyond Denmark.
Practice Implications
- ADHD and autism are different today, and the reason likely has to do with changes in how we apply diagnostic criteria and cut-offs for severity.
- Learn more about how autism criteria have changed, and how to apply the criteria in high-functioning adults.
—Chris Aiken, MD
Director, Psych Partners
Editor in Chief, Carlat Psychiatry Report
