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

The summarized studies indicate an increased frequency of minor facial anomalies in individuals with ASC compared to TD individuals [Ozgen et al., 2011, 2013; Rodier et al., 1997; Walker, 1977]. Among the features examined, facial asymmetry in ASC appears to exhibit the greatest consistency between studies [Hammond et al., 2008; Ozgen et al., 2011, 2013]. There is also some evidence to suggest that ASC-related facial characteristics may correspond with particular cognitive and behavioral traits. Specifically, reduced maxillary height and increased mouth width may be more common among individuals with ASC who have comorbid intellectual disability, language regression, and greater severity of ASC symptoms [Aldridge et al., 2011; Obafemi-Ajayi et al., 2015]. Findings from one study suggest that decreased mouth width may be more common among individuals with ASC who have an IQ within the normal range and lower symptom severity [Obafemi-Ajayi et al., 2015]. However, these conclusions must be considered preliminary given that the studies in this area have overlapping participant samples.