Why Autism Looks Different Today

The autism diagnosis has changed, and this study reveals a big reason why

STUDY: Salkić A et al, Psychiatry Research 2026

STUDY TYPE: Cohort study

FUNDING: Skaraborg Hospital, FORTE, Craafordska Foundation, ALF, Swedish Research Council, Marcus and Amalia Wallenbergs Foundation

Background

In the 1960s and 70s, about 70% of people diagnosed with autism also had intellectual disability. That figure has been falling ever since, and this study tracks the change.

The Study

• 81,286 patients with autism diagnosed in Sweden between 2001 and 2020
• Intellectual disability was identified through psychiatric registers and a national school database

The proportion of autism diagnoses that included an intellectual disability fell from 55.8% in 2001 to 6.7% in 2020. Autism diagnoses overall increased 800% over the same period.

The trend held in both females and males and persisted even when the analysis was restricted to children. Children diagnosed before age 7 still had higher rates of intellectual disability (around 15% by 2020), consistent with the idea that earlier diagnosis tracks with more severe symptoms.

Practice Implications

1. Earlier, I reviewed how the definition of autism has changed over the years, but that doesn’t explain this trend.
2. In the past, society had a higher bar of severity to make this diagnosis, or to refer to a child psychiatry center, which may explain this rise in autism with intact IQ.