Investigating facial phenotype in autism spectrum conditions: The importance of a hypothesis driven approach

Atypical facial characteristics have been observed in many disorders associated with developmental disability. While autism spectrum conditions (ASC) have not previously been thought to be associated with a distinct facial phenotype, an emerging research literature is casting doubt on this assumption. The identification of differences in the facial phenotype of individuals with ASC may contribute to efforts to promote early identification of the condition and help elucidate etiological pathways. With the aim of identifying facial phenotypes associated with ASC, this commentary evaluated facial features purported to distinguish ASC from typical development. Although there is little consensus across the reviewed studies for the majority of facial characteristics described, preliminary evidence suggests increased facial asymmetry may be more common in ASC. There is also evidence to suggest that there are morphologically distinct subgroups within ASC that correspond with different cognitive and behavioral symptomatology. However, in light of the various inconsistencies in the reported literature, and based on an accumulating understanding of etiological pathways proposed to be associated with ASC, we propose an alternative paradigm for investigating facial phenotypes in ASC. A series of studies are outlined to demonstrate the promise of a research program that has taken a hypothesis-driven approach to examine facial phenotypes associated with increased exposure to prenatal testosterone and to ASC. Autism Res 2017, 10: 1910–1918.