In pursuit of neurophenotypes: The consequences of having autism and a big brain.
David G Amaral, Deana Li, Lauren Libero and 6 others
PMID 28239961WHAT IT FOUND
Boys with autism and very large brains were more likely to have IQ under 70 and low language by age 5, while autism severity scores were similar.
Key findings
01At the later assessment, boys with autism and very large brains had lower mean IQ and a higher percentage with IQ under 70 than boys with autism and normal brain size.
02At first assessment, 74% of boys with autism and very large brains had low language, compared with 45% of boys with autism and normal brain size.
03Autism severity scores did not differ between the large-brain and normal-brain autism groups at either assessment, and were not correlated with brain size.
STILL TO COME
How it was doneWhat they foundWhat it means for OTsWhat it means for SLPs
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What it does not show
This is a commentary reporting cohort data, not a treatment trial, so it cannot show that any therapy works. The large-brain group was small: 19 boys at Time 1, 15 at Time 2, and 11 at Time 3. The analysis focused on boys, and the paper says girls are under-represented. Detailed methods are not fully reported here and are referred to previous publications. The large-brain definition is based on a brain size to height ratio 1.5 standard deviations above typically developing boys. No difference in autism severity was found, so brain size does not map simply to autism symptom severity. IQ differences appeared by age 5 but were not present at age 3, so early brain size alone did not predict the later IQ difference. Some children improved and others did not, so group means hide individual variation. Genetic and maternal antibody findings are preliminary and do not separate the groups consistently.
Declared interests
The authors declared no conflicts of interest. The supplied text does not name a funder.
The easy way to misread this
Do not conclude that a large brain causes autism symptoms or that these boys need a specific therapy. The study observed boys with autism and very large brains, did not test treatment, and found no difference in autism severity scores.