Prevalence of pervasive developmental disorder in Down's syndrome.

Lowenthal et al. (2007) counted how many people with Down syndrome also have a pervasive developmental disorder (PDD).

They looked at a group of individuals with Down syndrome and checked who met the rules for PDD or autism.

About 1 in 6 had some form of PDD. About 1 in 20 had autism.

These numbers help you plan screening and services.

Dargue et al. (2021) pooled 125 single-case ABA studies and found medium gains in communication and challenging behavior for people with Down syndrome. Rosane gives the prevalence base; Nicole shows ABA can help once you know the child is there.

Sisson et al. (1993) found even higher PDD rates in tuberous sclerosis: 1 in 4 for autism and almost 1 in 2 for any PDD among kids with intellectual disability. Both papers say the same thing: check for dual diagnoses in genetic conditions, just the numbers differ.

de Bildt et al. (2003) tested two quick screeners for PDD in intellectual disability. Pairing their tools with Rosane’s rate tells you who to screen first in your Down-syndrome caseload.

If you serve clients with Down syndrome, expect PDD in about 16%. Start universal screening, then use ABA as Nicole’s meta shows it works for this group. Add the ABC and PDD-MRS for a fuller picture.