A different ‘different’: the female presentation of Autism spectrum disorder and implications for detection and diagnosis

Author: Joanna Tsirgiotis

  • Thesis download: available for open access on 7 Dec 2022.

Tsirgiotis, Joanna Madeleine, 2020 A different ‘different’: the female presentation of Autism spectrum disorder and implications for detection and diagnosis, Flinders University, College of Education, Psychology and Social Work

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Autism spectrum disorder (ASD) is diagnosed more commonly among males than females (Loomes et al., 2017). Although females may be less likely to develop the condition due to biogenetic protective factors (Robinson et al., 2013), growing evidence suggests that a large number of autistic females remain undiagnosed and are thus unable to access the specialised support they may require (Hull et al., 2020). This thesis examines potential reasons for the underdiagnosis of females with ASD, with a particular focus on fine-grained behavioural differences between males and females and possible bias related to the interpretation of autistic behaviours.

In order to investigate the specific behaviours and domains in which males and females differ in the severity of their ASD difficulties, in Study 1, I analysed item-level profiles of 777 children using the Childhood Autism Rating Scale, 2nd Edition (CARS2; Scholper et al., 2010) or Gilliam Autism Rating Scale, 3rd Edition (GARS-3; Gilliam, 2014). Males demonstrated greater difficulty in six CARS2-ST items and seven specific behaviours on the GARS-3, most of which reflected specific restricted and repetitive behaviours. Across all instruments, the only area in which females showed greater difficulty was fear or nervousness (CARS2-ST). No meaningful differences emerged from the CARS2-HF analysis. On the items where males showed greater difficulty, females were more likely to present with developmentally typical behaviour.

Study 2 was comprised of two parts, each of which addressed the issue of why some females with many ASD traits are not diagnosed with ASD when they present for assessment. In Study 2a, I explored changes in the presentations of 12 girls who were diagnosed with ASD only after an initial negative result. A number of specific social difficulties emerged between assessments, particularly in the content of conversation. Further, there was a meaningfully higher probability that they would meet Criterion B2, insistence on sameness, routines, and ritualised behaviour at the time of the second assessment. In Study 2b, the presentations of both males and females who were either diagnosed with ASD (n = 156) or not diagnosed with ASD despite many ASD traits, being suspected of having ASD, and being referred for assessment (n = 78), were compared. Two important contributions of Study 2b were: (a) the inclusion of females whose presentation deviates from the classic male conceptualisation, did not meet criteria and remained undiagnosed (often excluded from the research to date), and (b) consideration of diagnostic data from different report sources: parent report, diagnostic observations, and teacher report. Results showed that females were less likely than males to meet Criterion B3 (restricted interests), and this was especially the case for subclinical (non-ASD) females. Indeed, of all criteria, females who presented due to ASD concerns and were either diagnosed or not diagnosed, were least likely to meet Criterion B3. Evidence of sex/gender specific restricted interests and stereotypical behaviours was found. Further, teachers and diagnosticians were less likely to report concern for females than for males. Importantly, many behaviours differed in the extent to which they predicted the ASD diagnostic result for males and females, perhaps suggesting that sex/gender influences how ASD-related behaviours are perceived.

In Study 3, 47 ASD diagnosticians were presented with two hypothetical case studies (one male ASD presentation and one female ASD presentation), and the sex/gender of the child described was randomly assigned within each. Diagnosticians reported greater ASD symptom severity when female sex/gender pseudonyms were allocated to the case studies, but their confidence in ASD diagnosis was similar regardless of the sex/gender condition. Diagnosticians identified a large number of challenges associated with assessing females for ASD. Many of these related to sex/gender differences in ASD presentation and difficulties in detecting the presentation of females. Broadly, results provided new insight into why ASD may be under-identified and underdiagnosed among females and provide evidence to support a broader and/or clearer and more flexible conceptualisation of ASD in order to better reflect the difficulties of autistic females and promote greater diagnostic certainty.

Keywords: Autism spectrum disorder, autism, sex differences, gender differences female presentation, female phenotype

Subject: Psychology thesis

Thesis type: Doctor of Philosophy
Completed: 2020
School: College of Education, Psychology and Social Work
Supervisor: Professor Robyn Young