The importance of low IQ to early diagnosis of autism.
Kristina Denisova, Zhichun Lin
PMID 36373182WHAT IT FOUND
Infants and toddlers later diagnosed with autism had lower early cognitive scores than typically developing peers.
Very low scores before 1 year were associated with a higher risk of later diagnosis.
Key findings
01At each age bin tested, full-scale IQ ranks were significantly lower in children later diagnosed with ASD than in typically developing children.
02Infants whose first full-scale IQ score was below 2 SD had a higher risk of later ASD diagnosis, including infants under about 1 year of age.
03Lower full-scale IQ scores were significantly associated with worse social, non-social, and total autism severity scores on the ADOS.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study found associations, not causes. It cannot show that low IQ causes autism or that low IQ alone leads to an autism diagnosis. The sample came from children involved in NIH-funded autism and development research, so it may not represent all children with autism or all typically developing children. The Mullen norms have not been updated in several decades, although the scores correlated with DAS-II scores in a subset. The early risk finding before 1 year was significant for male infants but not female infants, and the authors note small numbers of female infants at 6 months. The adaptive functioning findings were exploratory and focused on outlier cases, so they are not a main diagnostic finding.
Declared interests
The authors declared no conflict of interest. The study used data from NIH-funded studies, and the funding statement lists the Simons Foundation and the National Institutes of Health.
The easy way to misread this
Do not read low IQ as a cause of autism or as a standalone diagnostic test. The study only reports that early low cognitive scores were associated with later ASD diagnosis and worse symptoms, and it cannot show why those scores were low.