Gender Bias in Autism Spectrum Disorder – Lack of Research or Biology?

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It is unfortunately not uncommon for girls and women with autism to be misdiagnosed, mislabeled or ignored entirely. Autism spectrum disorder (ASD) is often seen as a male-dominant condition. Adolescent boys are still four times more likely to be diagnosed with ASD than girls with symptoms of similar severity. There is however some level of cognizance for this gender-bias today, among researchers and clinicians.

Recent research based on active screening suggests that female-to-male ratio of ASD patients should be as low as 1 female to 2 males; this is as opposed to the traditional 1:8 ratio, when clinicians use tailored diagnostic criteria for girls and women. This suggests that the number of males and females with autism is far more congruent than previously believed; highlighting the need for female autism research and tailored diagnostic processes.

So, why is there gender-bias within Autism diagnoses?
The factors underlying this gender inequality are not fully understood. Some suggest that the disproportionately small numbers of diagnosed autistic females is due the lack of female-based autism research, while other researchers argue that the higher rates at which autistic boys are diagnosed, reflect the increased likelihood of males developing ASD.

Inherent Assumption and Lack of Female Research
In autism research, much of our knowledge is exclusively drawn from male populations, as the researchers that investigated ASD initially assumed it was a male-exclusive phenomenon. In 1938, Hans Asperger first theorised autism under the assumption that it predominantly affects males. His studies, which played an important role in creating the modern diagnostic criteria for ASD, were also done exclusively on boys.

Due to these early assumptions about ASD, subsequent studies have continued to study male-only populations, magnifying the gender-bias.
This has also meant that the most of what we know about Autism today reflects in what we know and understand only about about male autism.

While we know that ASD affects individuals in different ways, the differences in autism presentation between males and females are still being investigated.

Studies have found that females with ASD can pay greater attention to social situations and cues, and are therefore better at masking their autistic traits by observing the behaviours of their neurotypical peers. They often also have fewer repetitive behaviours and more socially ‘acceptable’ and ‘mainstream’ types of interests, which are often missed or mistaken as fandom.

Comorbidities such as anxiety and depression are also reported more frequently in autistic females compared to males, making autism diagnosis in females that much more complex. These differences, combined with the limited research around females, and the lack of clear diagnostic criteria based on female ASD characteristics, have made it difficult to detect autism in young girls and women.

Biology
On the other hand, recent studies have suggested that perhaps the prevailing assumption of autism being a male-driven condition, and of course, the subsequent lack of research are not the sole factors for the imbalance in male-to-female ratio in ASD. Arguments have been made that there is in fact a variability in the disease susceptibility in sexes that must be addressed. A recent comparative study by researchers in New Hampshire found that male and female brains show different autism-related gene expressions and protein regulation patterns. In the female brain, these proteins were found to be more strongly regulated than in males’ brains – which could possibly help prevent the development of ASD in females.

Other studies have suggested that oxytocin and female sex hormones play a crucial role in the reducing susceptibility to ASD development. Interestingly, these hormones, previously linked to promoting pro-social behaviours and reducing social anxiety, are expressed in higher concentrations in the female foetus at critical developmental stages.

Another theory that may explain the gender-bias in ASD is that in development, male foetuses are more vulnerable to prenatal insults (such as stress, malnutrition, or infections), which are associated with increased susceptibility to genetic mutations relevant to autism. Further research is needed to explain the role of these theories in the development of ASD in both the female and male brains.



How does this gender bias affect girls and women with undiagnosed autism?
While historically our understanding of autism has been purely from the male perspective, more clinicians and researchers are gaining awareness of the gender-bias in autism. More females are being diagnosed and recruited into research studies, deepening our understanding of female-autism and increasing their representation in autism research.

That aside, there are still many practical reasons that inhibit researchers from investigating more autistic females and working towards bridging this gap. These may include difficulty to recruit girls and young women with ASD, due to the flawed diagnostic process and limited numbers of diagnosed female patients. Another thwarting factor could be that studying ASD girls and women may introduce confounding factors that could skew that data as female and male disease presentations are heterogenous.

That being said, in the interest of helping women and girls understand and navigate issues stemming from a misdiagnosis or a lack of diagnosis itself, researchers should continue to aim to include females with ASD in their quest to understand the complexity of this condition.

Interestingly, a study found that 23% of all women hospitalised with anorexia nervosa meet the diagnostic criteria for ASD. Furthermore, a failure to include these girls and women in research also leads to a magnified gap in knowledge.

Failing to diagnose girls in their early years often means that women diagnosed in their 20s, 30s or even 40s are left with no support, since much of the support offered to those with ASD is offered to children and young adults. This is known to cause negative effects on the mental health of these women.

It is only with increased efforts from researchers coming together and compiling multi-site female-related data, and clinicians gaining awareness of how ASD can manifest in females, that we address this gender inequality and provide girls and women with the agency they deserve.

Some helpful resources:
Marianne had always felt different. Yet, she wasn’t diagnosed with ASD until she was 27. This is her experience: https://www.nytimes.com/2020/12/05/opinion/autism-adult-diagnosis-women.html?ref=oembed

Nicola was diagnosed in her late 40s. This is her story:
https://www.theguardian.com/commentisfree/2016/aug/30/diagnosed-autism-male-condition-women-misdiagnosed

Sources referred in the article:
Zhou, Y., Qiu, L., Sterpka, A., Wang, H., Chu, F., & Chen, X. (2019). Comparative Phosphoproteomic Profiling of Type III Adenylyl Cyclase Knockout and Control, Male, and Female Mice. Frontiers in cellular neuroscience13, 34. https://doi.org/10.3389/fncel.2019.00034

Westwood, H., Mandy, W., & Tchanturia, K. (2017). Clinical evaluation of autistic symptoms in women with anorexia nervosa. Molecular autism8, 12. https://doi.org/10.1186/s13229-017-0128-x

Featured photo source: Edward Jenner from Pexels.

Edited by Malavika Ramanand

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