Professionals in the field have for many years given thought as to why there are so many more boys than girls diagnosed with Autism Spectrum Disorder (ASD). The generally accepted ratio of four boys to every girl rises to around 10:1 in ‘high functioning’ Autism or Asperger Syndrome (AS). Incidence ratios as high as 15:1 and 16:1 have also been reported in certain populations. At first glance these findings would suggest that girls are less likely than boys to develop ASD. However, there is a growing consensus that differences in diagnostic rates may have more to do with external cultural factors than significant differences between boys and girls. In this article we will discuss the various factors that have contributed to the current gender bias in ASD diagnoses.
The maleness of Autism
In 1943, Leo Kanner published a case study of 11 children displaying behaviour he described as Autistic. These observations are credited as being the first documented cases of Autism in the United States. However, in Europe at much the same time, Austrian paediatrician Hans Asperger—unbeknown to Kanner—had become interested in a group of patients displaying behaviour he would later serendipitously describe as Autistic. However, the view of Autism that Asperger would form was considerably broader than Kanner’s Autism. Asperger saw Autism in patients of all ages, in people with and without intellectual disability, and critically for our discussion today Asperger believed both males and females can have Autism. However, in his classic 1944 paper Asperger noted his uncertainty about Autism in females:
In the autistic individual the male pattern is exaggerated to the extreme…It could be that autistic traits in the female only become evident after puberty. We just don’t know (Frith, 1991).
Tragically, Asperger’s work remained hidden for much of the 20th century, in part due to the international communities rejection of scientific literature published in the midst of the Nazi occupation. Consequently Kanner’s narrower, much more male centric view of Autism prevailed and dominated much of the academic thought in the years that followed.
Their different ways
While Autism is often considered in terms of hyper-male characteristics, girls and boys with ASD present with many similar characteristics. They will all have some degree of difficulty relating to and communicating with others. They may all have a particular behaviour that is repeated over and over again, or follow special interests with an intensity that may be considered extreme. However, some characteristics may present slightly differently in girls. In general, the girl with ASD might appear more passive and with better social communication skills—as in a stereotype of the typical female. Girls are generally more able to speak about their feelings and are less prone to challenging behaviour than boys. Among the general population it is often thought that boys do ‘act out’ more than girls; and children who show aggression are more likely to be referred to a clinician for advice on behaviour management, and to determine if the behaviour is due to a developmental disorder (Attwood, 2006).
What part do genes play?
It has been suggested that the difference in gender ratio could be influenced by protective genetic factors that make it less likely that a female will display autistic behaviour than a male (Skuse, 2000). A recent study recruited 10,000 pairs of fraternal twins to see if siblings of females with Autism displayed more autistic traits than siblings of males (Robinson et al. 2013). They suggest the presence of these autistic traits is a marker for higher genetic risk within the family. Results supported their hypothesis that biological risk factors are greater in the families of females with Autism. This finding suggests that a higher genetic risk is required for females to receive a diagnosis of Autism, than for their male counterparts. One of the research team, Dr Ronald, stated “unless the girls were loaded up to the gills with genetic risk factors, they did not have many of the autism symptoms” (cited by Ernsperger, L). However, despite multiple promising genetic and neuroimaging studies no biological basis for Autism has been agreed upon. As we can see, genetics will inevitably play an important role in future explanations of male/female ratio differences.
Why ASD in girls may not be readily recognised:
Passivity may not be recognised as social impairment.
It is socially acceptable for girls to be quiet and introverted.
Girls may not draw attention to themselves as boys with ASD are likely to do, causing disruption in the classroom.
Girls with ASD who have difficulty with eye contact may be considered shy or naïve, rather than this feature of ASD being recognised (Attwood and Grandin, 2006).
It has also been noted that girls with AS may be more difficult to recognise due to the camouflaging and coping methods they may adopt, employed by some boys in the same way. They might use their intellect to engage socially—rather than natural ability—watching and listening before attempting to join in. They might adopt a social persona, a script, based on someone they perceive to be worthy of copying (Attwood, 2006). Brief contact with the person who is ‘acting’ a personality may not reveal anything unusual.
The special interest of a girl with ASD might appear to be very similar to that of any typically developing young girl. They might both love Barbie dolls or have a passion for horses and ponies. However, the way that they engage with their interest is likely to be different. The girl with ASD is likely to arrange her dolls in a particular, never changing, way and unlikely to share them with friends for play. She may use the dolls to represent figures in her life—they may become alternative to real friends. They may be used to rehearse what to say in anticipated situations. The interest could be solitary and functional (Attwood, 2006). Attwood describes the way that the special interest in an animal can sometimes develop to such an extent that the child begins to act like the animal that provides a substitute for a real friend—one that is non-judgemental and does not tease.
Is it more difficult for a female to receive an ASD diagnosis?
The male/female ratio changes significantly from 4:1 and higher when additional behavioural and/or learning problems are evident in girls; it may be as close as 2:1. This could suggest that ‘high functioning’ women and girls with Autism are being missed with diagnosis. Many commentators are posing the question: are current diagnostic criteria and practices biased toward a male stereotype, making it more difficult for a female with ASD to receive the diagnosis? If a girl presents with no intellectual impairment or obvious behavioural problems, a diagnosis appears far less likely. If this is the case many women and girls could be missed through the current diagnostic process, missing out on valuable support services, enabling them to live fuller and richer lives.
A script for diagnostic assessment
In order to address the concerns raised, new screening and assessment tools are being developed and designed, mindful of the differences in male/female presentations of ASD. One such tool, The Girls Questionnaire for Autism Spectrum Disorders (Attwood, Garnett & Rynkiewicz, 2011) was developed by Dr Tony Attwood and colleagues over a number of years, here in Australia. The work, since renamed Q-ASC Questionnaire for Autism Spectrum Conditions Age 5 – 19, was presented at IMFAR (International Meeting for Autism research) in May this year in San Francisco. The questionnaire is recommended for use as a screening tool—a script for diagnostic assessment—not for a diagnosis. At the time of writing, a scoring system for the questionnaire is still to be developed. Currently, the research and validation is being finalised in Australia in collaboration with other international parties.
International efforts are beginning to draw attention to the needs of women and girls with Autism. These efforts are being led by prominent women with Autism, including the eminent Dr Temple Grandin and Dr Emma Goodall. However, more work is needed to understand the expression of Autism in females. What are the similarities and differences between males and females, and what implications do they have for diagnosis and intervention? We look forward to much more research in this space.
Attwood, T., (2006) The Complete Guide to Asperger’s Syndrome. Jessica Kingsley Publishers. London & Philadelphia.
Attwood, T., Garnett, M. S. & Rynkiewicz, A. Q – ASC Questionnaire for Autism Spectrum Conditions Age 5 – 19. Retrieved from: http://spectrumascmed.com/wp-content/uploads/2016/08/Fragment-Q-ASC.pdf
Attwood, T. & Grandin, T. (2006) Asperger’s and Girls. Future Horizons. Arlington, TX.
Dworzynski, K., Ronald, A., Bolton, P. F. & Happe, F. (2012). “How Different are Girls and Boys above and Below the Diagnostic Threshold for Autism Spectrum Disorder?” Journal of the American Academy of Child & Adolescent Psychiatry 51(8): 788-797.
Ernsperger, L. (2014) “Girls and women on the Autism Spectrum”. Retrieved from http://www.amaze.org.au
Frith, U (Ed.) 1991. Autism and Asperger Syndrome. Cambridge University Press. Cambridge UK.
Ormond, S., Brownlow, C., Garnett, M.S., Rynkiewicz, A., & Attwood, T. (2017). Profiling Autism Symptomatology: An Exploration of the Q-ASC Parental Report Scale in Capturing Sex Differences in Autism. Journal of Autism and Developmental Disorders. https://doi.org/10.1007/s10803-017-3324-9
Robinson, E. B., Lichtenstein, P., Anckarsäter, H., Happé, F. & Ronald, A. (2013). Examining and interpreting the female protective effect against autistic behaviour. Proceedings of the National Academy, doi: 10.1073/pnas. 1211070110.
Skuse, D.H. (2000). Imprinting, the X-chromosome, and the male brain: Explaining sex differences in the liability to autism. Prediatr Res, 47(1): 9-16.
The National Autistic Society: http://www.autism.org.uk/