A quarterly publication of the Autism Research Institute

The Autism Research Review International is quarterly publication of the Autism Research Institute

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Facial features of siblings of children with autism offer evidence of broad autism phenotype

The facial features of both male and female siblings of children with autism spectrum disorders (ASD) tend to be more masculine than the features of sex- and age-matched controls, according to a new study that offers support for the idea that there is a broad autism phenotype. In addition, the study is consistent with the “extreme male brain” hypothesis, which links ASD to elevated exposure to testosterone in the womb. 

In earlier research, Diana Weiting Tan and colleagues found that both male and female children with ASD tend to have a masculinized facial structure. In the new study, they used 3D facial photogrammetry to analyze the facial features of 55 non-autistic siblings (30 boys and 25 girls) of children with ASD, comparing them to age-matched children without siblings with ASD. 

The researchers found that the facial features of male siblings were significantly more masculine than the features of male controls. The facial features of female siblings were also more masculine than the features of female controls, but to a lesser degree. 

The researchers say the patterns they detected are consistent with the findings of a recent study that examined levels of autistic traits measured using the child version of the Autism-spectrum Quotient (AQ-Child). On that scale, they say, there was no difference in scores between male children with ASD and their non-autistic male siblings, with both groups scoring higher than controls. The scores of non-autistic girl siblings fell between the scores for their female siblings with ASD and controls. 

The researchers conclude, “The current study presents the first evidence for facial masculinity to express as a broad autism phenotype. This finding builds upon prior evidence linking prenatal testosterone exposure to postnatal facial masculinity and corroborates the ‘extreme male brain theory’ that ASD may be, in part, linked to elevated levels of testosterone in utero. More broadly, these data suggest that facial masculinity is a feature of ASD that is likely to be connected to genetic influences.”


Citations

“A broad autism phenotype expressed in facial morphology,” Diana Weiting Tan, Murray T. Maybery, Syed Zulqarnain Gilani, Gail A. Alvares, Ajmal Mian, David Suter, and Andrew J. O. Whitehouse, Translational Psychiatry, January 2020 (free online). Address: Diana Weiting Tan, School of Psychological Science, University of Western Australia, Perth, Australia, [email protected].