Autism and related disorders: epidemiological findings in a Norwegian study using ICD-10 diagnostic criteria.
Strict ICD-10 rules once missed most autistic children; modern counts are twenty times higher.
01Research in Context
What this study did
Gaily et al. (1998) counted every child in Norway who met strict ICD-10 rules for childhood autism.
They searched medical records across the whole country to find how many kids had the diagnosis.
What they found
Only 4–5 children in every 10 000 met the tight ICD-10 label.
That number felt low even at the time.
How this fits with other research
Zeidan et al. (2022) now says the world median is 100 per 10 000—twenty times higher.
The jump does not mean more kids are sick; it means we now count milder traits and use wider tools.
May et al. (2020) got 436 per 10 000 using parent reports, showing the leap happens when you ask families instead of only hospital charts.
Why it matters
If you screen with old ICD-10 rules you will miss most autistic learners.
Use current tools and broader criteria so kids get help earlier.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Add a parent questionnaire like the AQ-10 to your intake packet—do not rely only on medical codes.
02At a glance
03Original abstract
Recent studies of the prevalence of autism have suggested higher estimates than previously described. Various diagnostic criteria for autism and related disorders have been applied, with variability in case finding methodology and characteristics of populations as well. In this study, maternal and child health clinics covering 98% of the population were used for screening pervasive developmental disorders. Extensive medical investigation was carried out on the majority of cases. In this Norwegian population of children ages 3-14 years the minimum prevalence estimate for childhood autism was 4-5 per 10,000 using ICD-10 research criteria, and did not confirm the high estimates suggested more recently. Medical disorders identified were associated with mental retardation rather than specifically with autism.
Journal of autism and developmental disorders, 1998 · doi:10.1023/a:1026017405150