More masculine faces in Autistic children?

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Elevated prenatal testosterone exposure has been associated with Autism Spectrum Disorder (ASD) and facial masculinity. By employing three-dimensional (3D) photogrammetry, the current study investigated whether prepubescent boys and girls with ASD present increased facial masculinity compared to typically-developing controls. There were two phases to this research. 3D facial images were obtained from a normative sample of 48 boys and 53 girls (3.01–12.44 years old) to determine typical facial masculinity/femininity. The sexually dimorphic features were used to create a continuous ‘gender score’, indexing degree of facial masculinity. Gender scores based on 3D facial images were then compared for 54 autistic and 54 control boys (3.01–12.52 years old), and also for 20 autistic and 60 control girls (4.24–11.78 years). For each sex, increased facial masculinity was observed in the ASD group relative to control group. Further analyses revealed that increased facial masculinity in the ASD group correlated with more social-communication difficulties based on the Social Affect score derived from the Autism Diagnostic Observation Scale-Generic (ADOS-G). There was no association between facial masculinity and the derived Restricted and Repetitive Behaviours score. This is the first study demonstrating facial hypermasculinisation in ASD and its relationship to social-communication difficulties in prepubescent children

The current study employed a two-step approach, first determining a set of facial features that could distinguish faces of boys and girls. These features were then used to investigate the hypermasculinisation and androgyny accounts by comparing children with and without ASD on facial masculinity/femininity. The present findings provide support for the hypermasculinisation account in which increased facial masculinity was observed in the overall facial structure and in individual features of autistic boys and girls in comparison to typically-developing controls.

Research to date, including the current study, indicate a stable pattern of results for females in which hypermasculinised facial appearance has been reported in prepubescent girls with ASD (in the current study) and in women with ASD28 compared to their typically-developing counterparts. However, the association between facial masculinity and autistic behaviours has been less consistent for males. While the current study found clear evidence for hypermasculinised facial features in boys with ASD, Bejerot et al.28 did not observe a difference in the facial features of autistic and non-autistic men. We raise two possibilities for the discrepant findings between the two studies.

First, there were considerable differences between studies in the methodologies used to examine facial features. Bejerot et al.28 took two-dimensional facial photographs of autistic and non-autistic adults, and had eight naïve observers rate each face for ‘gender coherence’, whereas the current study used landmark data from 3D images of autistic and non-autistic children to create objective measurements of sexually dimorphic facial features. Although existing evidence suggests that the subjective ratings of facial masculinity/femininity and the combined use of linear and geodesic measurements are positively correlated36, the study undertaken by Bejerot et al.28 did not directly examine masculinity/femininity. The authors interpreted low gender coherence ratings as being less feminine for females and less masculine for males, but the connotation of “gender coherence” is arguably ambiguous, that is, a less gender typical face could indicate an extremely high or an extremely low degree of masculinity/femininity. Second, the current study employed 3D photogrammetry which measures facial shape with submillimetre accuracy. It is possible that this high measurement precision identified more subtle sexually dimorphic effects that are unable to be observed through subjective ratings. Bejerot et al. did report subjective ratings of increased masculinity (or androgyny) in adult females with ASD, which suggests the possibility that increased facial masculinity in males with ASD may be a more subtle effect than that observed in females with ASD.

Nevertheless, despite using similar methodology as the one described in Gilani et al.26, the outcomes of the current study run counter to the findings reported in Gilani et al.26 in which more androgynous features were found in neurotypical adults with higher levels of autistic traits. An important difference between the two studies is that the current study investigated pre-pubertal children, whereas Gilani et al.26 (and also Bejerot et al.28) examined post-pubertal adults. The surge of serum testosterone concentrations during puberty is 20–30-fold higher in males compared with females45, and previous studies of general population samples have found that salivary testosterone levels of 12–18-year-olds are related to sexually dimorphic facial features31. While recent evidence suggests that prenatal testosterone exposure has a greater influence than postnatal testosterone on facial morphology in adulthood24, the influence of pubertal testosterone cannot be ruled out. One further possibility for the discrepant findings relates to the differences in how Gilani et al.26 and the current study measured facial distances—Gilani et al.26 measured linear distances between two facial landmarks while the current study included both linear and geodesic distances. The use of both linear and geodesic distances provides considerably higher measurement precision. Furthermore, eight of 11 distances that were identified as sexually dimorphic in Study 1 were geodesic distances. Future studies examining both linear and geodesic distances in adults with ASD will build on the findings presented here.

An important secondary finding of this study was the relationship between facial masculinity and ASD symptom severity in prepubescent boys and girls. For both sexes, an association was identified between hypermasculinised facial features (indicated by lower gender scores) and social-communication difficulties but not restricted interests and repetitive behaviours, assessed using the ADOS-G. Consistent with the current study, Obafemi-Ajayi et al.35 observed that autistic boys with more profound social-communication difficulties were characterised by facial features such as increased facial height and mouth width, and decreased mid-face height. However, in contrast to the present study, Obafemi-Ajayi et al.35 also reported an association between facial morphology and the extent of restricted interests and repetitive behaviours. One possible reason for the difference in findings relates to the difference in orientation of the two studies. Obafemi-Ajayi et al.35 focused on identifying a set of facial features in boys with ASD that deviated from those of typically-developing boys, whereas the current study framed hypotheses around the possible effects of prenatal testosterone on the levels of facial masculinisation in these two groups.

Taken together, these findings suggest that while facial phenotype specific to each behavioural domain of ASD exists, the underlying biological factors driving the development of each facial phenotype may differ. The current findings raise the possibility that prenatal testosterone has an effect on the development of atypical social-communication behaviours but exerts little influence on the restricted and repetitive behaviours in both boys and girls with ASD. Notably, ASD incorporates a high degree of phenotypic heterogeneity, and large population-based twin studies46 have found that the behavioural domains that characterise the condition have been found to be largely independent. The outcomes of the current study further highlight the importance of investigating aetiological factors in relation to the behavioural dimensions of ASD, rather than solely the categorical diagnostic entity47.

The 3D photogrammetry, measurements of linear and geodesic facial distances, two-phase validation protocol, individually-matched control samples and the inclusion of both sexes in the case-control study are the main strengths of the current study. However, we also acknowledge two limitations of our design. First, as both sample sizes in Study 1 and 2 are small, this limits our ability to generalise the current findings to the wider population. Nevertheless, sexual dimorphism in the three linear features have been previously reported in other studies41, 48. To the best of our knowledge, comparative data for geodesic measurements are not available in typically-developing children. Future research could perform the gender classification analyses (described in Study 1) using a larger sample to further examine sexually dimorphic facial features in the prepubescent population. Second, autistic-like traits were not assessed in the typically developing control group, thus it is possible that some control boys and girls may have had subclinical levels of autistic-like traits. However, since the gender scores and five of the six sexually dimorphic facial features differed significantly between the ASD and control groups for each sex, we do not believe the power of the current study was substantially compromised by the possible inclusion of controls with some level of autistic traits.

Given the existing evidence for the link between prenatal testosterone and facial masculinisation24 and the current findings on the association between facial masculinisation and ASD, it appears that prenatal testosterone may play a part in both ASD-related behaviours and morphological features. Unfortunately, data on prenatal testosterone were not available for the current samples, which limits our ability to draw firm conclusions on the hypothesised relationships. Further investigation that tracks longitudinal links between early testosterone exposure, postnatal facial morphology and the autism phenotype will provide more direct tests of the hypothesised relationships. As well as recording testosterone levels in either amniotic fluid or umbilical cord blood, it would be informative to assess peak testosterone levels in early infancy. Because the brain continues to develop after birth49, several studies have considered the effects of the peak in testosterone production around one to three months after birth (known as the mini-puberty period) on the extent of autistic traits later in childhood6, 50, 51. One of these studies reported a positive association between salivary testosterone in 3-month-old infants and autistic-like behaviours when they were 18 months old51 whereas the other two studies identified no such relationship6, 50. Determining whether this early surge in testosterone has any effect on either autistic traits or facial morphology would augment research on prenatal testosterone and its effects.

Investigations into the facial structure of individuals of ASD have the potential to reveal greater insights into the biological pathways leading to autism. Facial phenotypes are widely used in the clinical diagnosis of numerous neurodevelopmental and other disorders, and provide an important research tool for identifying rare diseases and links between genotype and phenotype. The current study adopted an hypothesis-driven approach to investigate the influence of one potential etiological factor on facial phenotype—prenatal testosterone exposure—as well as links between facial and behavioural phenotypes. However, we also see merit in adopting an hypothesis-free approach in examining differences between the ASD and typically-developing populations. Larger sample sizes will be critical to achieving this aim and understanding more about the etiological pathways underpinning ASD.

Boys and girls with ASD were found to have more masculine facial features compared to age-matched typically developing controls, and increased facial masculinity was related to greater severity of social-communication behaviours. While the current evidence for the association between ASD and prenatal testosterone exposure is mixed, the present study extends on a recent finding linking elevated prenatal testosterone and increased facial masculinity2

I dont look masculine and it bothers me and today i read that is linked to aspergers ? Why do i need to deal with all of this at once, i thought this was affecting the brain

https://www.psychologytoday.com/us/blog ... asperger-s