Differences in the clinical presentation of Trisomy 21 with and without autism.
Autism can ride on top of Down syndrome—score ADI-R domains after accounting for IQ to spot it.
01Research in Context
What this study did
The team looked at one child with Down syndrome plus autism and one child with Down syndrome only.
They gave both kids the ADI-R interview. They compared scores after adjusting for IQ.
What they found
The child with both conditions scored worse on every autism domain. The gap stayed even after IQ was held constant.
This hints that autism in Down syndrome is a real extra layer, not just slow development.
How this fits with other research
Godfrey et al. (2019) later saw the same pattern in a bigger group. They added an ASD-only group and found that DS+ASD kids show equal social and repetitive-behaviour severity, unlike typical ASD where social issues dominate.
Amaral et al. (2017) conceptually replicated the finding with 25 DS+ASD children. They saw milder reciprocal-social deficits than in idiopathic ASD, supporting the idea of a unique DS+ASD profile.
Busch et al. (2010) looks contradictory at first: they report more behaviour problems in ASD than in DS. Their sample, however, was idiopathic ASD, not DS+ASD, so the studies actually describe different populations.
Why it matters
When you assess a child with Down syndrome, do not blame every social delay on low IQ. Use tools like the ADI-R and adjust for cognitive level. If scores still pass autism cut-offs, pursue autism services. This small case tells you that true autism can hide inside Down syndrome, and catching it unlocks more focused, effective interventions.
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02At a glance
03Original abstract
BACKGROUND: Autism occurs 10 times more often in children with Down syndrome than in the general population, but diagnosing co-occurring autism in Down syndrome with severe intellectual disability is challenging. The objective of this case-control study was to identify characteristics differentiating children with trisomy 21 with and without autism and to determine the extent to which severe cognitive impairment affects the measures of autism symptomatology. METHOD: Twenty children with trisomy 21 and autism (cases) were compared with children with trisomy 21 without autism (controls) matched on chronologic age, race and gender. Communication, cognitive and adaptive behaviour skills were assessed with standardized instruments. Medical history was reviewed and medical records were examined for early head growth. Scores on the diagnostic algorithm of the Autism Diagnostic Interview--Revised (ADI-R) were compared after adjusting for cognitive ability as measured by the Stanford-Binet (Fifth Edition) non-verbal change sensitive score. RESULTS: Cases performed significantly more poorly on all assessments. Mean case-control differences for matched pairs were all significant at P < 0.0001 for receptive and expressive language skills, cognitive skills and adaptive skills. Seven cases had a history of seizures compared with one control(P = 0.01). After adjusting for cognitive ability, the mean scores on the Reciprocal Social Interaction, Communication, and Restricted, Repetitive and Stereotyped Behaviours domains of the ADI-R diagnostic algorithm remained significantly higher in cases compared with controls (P < 0.0001). All participants had decreased head size consistent with Down syndrome, with no case-control differences. CONCLUSION: Children with trisomy 21 and autism have significantly more impaired brain function than children with trisomy 21 without autism. However, the deficits in the core domains of social reciprocity and communication, and the restricted and repetitive interests are not entirely explained by the more severe cognitive impairment. This autism phenotype in children with trisomy 21 which includes an increased risk for seizures may indicate a widespread loss of functional connectivity in the brain.
Journal of intellectual disability research : JIDR, 2009 · doi:10.1111/j.1365-2788.2008.01138.x