RESEARCH

Prevalence of autism spectrum conditions in primary schools (CAST)

Carrie Allison, Carol Brayne, Simon Baron-Cohen, Fiona Matthews, Sophia Sun

We developed the CAST, formerly known as the Childhood Asperger Screening Test but renamed as the Childhood Autism Spectrum Test. The change of name reflects that it was originally designed for a prevalence study of Asperger Syndrome in childhood but is useful for low-functioning children too. We found that the CAST discriminates cases from controls well, and that CAST scores show strong heritability in a twin study.

We used the CAST as a screening instrument in a large population study of 20,000 primary school age children in Cambridgeshire. Results confirm recent studies from other prevalence studies that autism spectrum conditions are found in about 1% of the population. This study also found for the first time that for every 3 known cases of ASC there are 2 undiagnosed cases. 

We have found associations between the CAST and foetal testosterone, and are exploring its relationship to a related screening instrument, the Autism Spectrum Quotient-Child Version. We are also now using the CAST in two new population studies, in China and in the Netherlands.