Has Autism Diagnosis Lost Its Meaning?

Uta Frith laid the groundwork for Theory of Mind research in Autism

A leading autism researcher argues today’s spectrum may actually be two different conditions wearing one label

STUDY: Frith U, Psychological Medicine 2026

STUDY TYPE: Editorial

FUNDING: Independent

Background

Autism first entered the diagnostic manuals in 1980, defined by social aloneness, language delay, and insistence on sameness. Each revision since has widened the net: Asperger disorder joined in 1994, and the 2013 manual folded everything into one spectrum that applies at any age or intelligence level, even when symptoms only show up by historical report.

Uta Frith, who helped shape the original criteria, now asks whether that widening has gone too far.

The Study

• Frith reviews population studies from the United Kingdom, Sweden, Denmark, and the United States spanning six decades.
• She compares people diagnosed in childhood with those diagnosed in adolescence or adulthood.
• She draws on genetic, sex-ratio, and comorbidity data to see whether these two groups still share a common core.

Prevalence climbed from 4 in 10,000 children in a 1966 UK survey to roughly 1 in 57 today, a 44-fold rise. Nearly all of that increase traces to people diagnosed later in life, especially women. The male-to-female ratio, stable at 3:1 to 4:1 for decades in childhood diagnoses, flattens to roughly 1:1 once diagnosis happens after age 15.

Intellectual disability, once present in over half of autism cases, now shows up in under 7%. A 2025 genetic study found the early-diagnosed group carries markers tied to social and repetitive-behavior traits, while the late-diagnosed group’s genetics overlap more with ADHD, depression, and PTSD, hinting these may be different conditions rather than the same one caught late.

Practice Implications

1. Late-diagnosed adult is likely different from a child who met criteria at age four.
2. Look for collateral information to make the diagnosis, and screen carefully for other disorders like bipolar, depression, ADHD, anxiety, schizophrenia, and PTSD before settling on the label.
3. Here’s more from the Mayo Clinic on how to diagnose high-functioning autism in adults.