What is the autism gender bias?
To correctly detail and discuss these topics, it is essential to understand that “sex” and “gender” are not interchangeable. Although they are viewed as such in basic science descriptions, the extrapolation into human studies has not been critically assessed (Hines, 2019). Within the holistic view of autism, “gender” refers to the range of characteristics, behaviors, and social structures that define the broader culture’s experience with femininity and masculinity. “Sex” (female or male) is based on chromosomes, gonads, hormones, and genitals and is a biological descriptive which does not consider lived experiences or the influence of social and cultural structures (Mulak et al., 2022; Hines, 2019). The term “sex/gender” is used in this article to describe instances where sex and gender influence the same aspect(s) of investigation or care.
Past theories on the autism gender ratio
Historically, much research has shown that males are more affected by autism than females. One of the most consistent findings in autism research has been the male-to-female prevalence ratio of 4:1 (Nordgren et al., 2018). This ratio and observed sex/gender differences have underpinned our comprehension of autism and simultaneously stumped researchers for decades. Explanations for these observations range from social reasoning to genetics. One prevalent theory explaining this observation is the Female Protective Effect (FPE), which posits that women have a higher carrying capacity for genetic information that links to autism. Therefore, “females are ‘protected’ from the combined effects of autism-linked genes, such that it takes a larger number of random genetic events for them to manifest autism traits” (Wigdor et al., 2022). FPE has been broadly tested, and results confirm and deny its credibility (Bai et al., 2020; Lewis et al., 2019).
Holistic understanding of the autism gender/sex bias
In tandem with major social and cultural shifts over the last decade, autism research has adopted a multi-disciplinary and holistic understanding of diagnosis and treatment. Consequently, researchers are reassessing the definitions and classifications that underpin autism literature and clinical practices. Within this expanded and more critical observation of the field, previous blind spots in how we define and assess autism have been brought to light. For example, autism is no longer understood as a pediatric condition. This paradigm shift allowed for the discovery of a “lost generation” of autistic adults who did not meet the criteria or have access to assessments and treatments in their youth. Research has further revealed that within this lost generation, self-diagnosed autistic adults are more likely to be women and female-presenting people, suggesting a skewed gender/sex ratio across generations (Lai & Baron-Cohen, 2015; McDonald, 2020).
“The understanding that autism can present very differently to how first imagined [was a critical shift in the last decade]. Many of the early studies that built the conception of autism were based on young, white males. Understanding how women may be diagnosed later and manifest their traits differently, has opened up a whole door to other research on intersectionality and better inclusion of all autistic people within the research.”
Dr. Hannah Belcher, autistic author and researcher (Communication 03/03/23)
Real-world outcomes for autistic women
The cycle of late and missed/misdiagnosis
Due to a historically incomplete description of autism (lacking the female, trans, non-binary… perspectives) and, therefore, biased diagnostic and assessment tools, practitioners have been predisposed to consider mental health issues in females as stand-alone conditions instead of co-occurring with autism. This often leads to misdiagnosing autism or missing an autism diagnosis in favor of a coexisting mental health issue. In fact, on average, women face a 10-year delay in receiving an autism diagnosis from the first time they present to mental health services. This is especially true for autistic women and female-presenting people who exhibit more nuanced autistic traits and do not have intellectual disabilities (Gesi et al., 2021).
“I think one of the most difficult parts [of receiving a late diagnosis] was really realizing how much I missed, how much I’ve been oblivious to throughout my whole life…And as soon as I realized that I could do things differently, [in ways] better suited to me and how my brain works, life got so much easier… I don’t hesitate now to make little adjustments if [something]’s causing me problems.”
Chris Nicholson, autistic home-decor store manager and single mother of two (Interview, 21/02/23)
Trauma and victimization
Autism is often characterized by differences in how individuals interpret and act during social situations, and research literature asserts that early interventions (as young as possible) yield the most positive results for autistic individuals. However, without a diagnosis and subsequent knowledge of autism traits, autistic girls and female-presenting people frequently lack self-understanding and are, therefore, unaware of their social and neurobiological differences. Such gaps in comprehension leave autistic females vulnerable to abuse, manipulation, and trauma, often for decades, as they walk the road to diagnosis (Zener, 2019). Research shows that autistic females are at three times the risk of coercive sexual victimization compared to their neurotypical peers and that autistic individuals have less sexual knowledge and experience more sexual victimization than neurotypical controls (Gotby et al., 2018; Brown-Lavoie et al., 2014). Another recent study identified an association between autistic traits, childhood abuse, trauma, victimization, and PTSD, where individuals with elevated autistic traits are at higher risk (Roberts et al., 2015). Without the understanding and support that generally accompany a diagnosis, autistic females often experience victimization, which leads to increased mental health difficulties and thus continues the cycle of missed/misdiagnosis (Jordan et al., 2010).
Masking, burnout, and suicidality
Masking, sometimes called camouflaging, is the conscious or unconscious adjustment and suppression of natural tendencies to “fit in” with social and cultural expectations. Techniques used for masking include forcing oneself to make eye contact, imitating social movements, scripting conversations, suppressing traits, and more (Pearson & Rose. 2021; Sedgewick et al., 2021). This and other forms of identity management frequently result from stigma and prejudice avoidance, a required part of daily functioning for many autistic individuals across their lifetime (Belcher et al., 2022a; Hull et al., 2017). Consequences of masking can include exhaustion, threats to self-perception, increased mental health difficulties, self-injurious behavior, autistic burnout, and suicidality (Hull et al., 2017; Cassidy et al., 2018; Miller et al., 2021).
“I used to sit next to a person or with a group of people for hours and be so uncomfortable, and everything was wrong, but I wouldn’t want them to know [and] I didn’t want to be difficult [or] cause a problem. So I would just sit there and just suck it up. And I realized that 90% of my life was sucking it up. And I’m like other people don’t do this! Other people will say ‘Hey, I don’t like the way I’m sitting, I’m gonna move.’ I would just sit there and be so uncomfortable. I was always afraid about being misunderstood.”
Chris Nicholson (Interview, 21/02/23)
Gender and masking
Investigations on the interaction of gender and self-reported masking relay contradicting findings. A recent study using the Camouflaging Autistic Traits Questionnaire (CAT-Q) found that autistic females self-reported higher amounts of masking than males but found no significant gender difference in scores for social compensation (Hull et al., 2020). Simultaneously, studies on the metrics and validity of camouflage assessments posit that, while the CAT-Q is a valuable baseline measurement tool, the psychometric properties of it and other masking rating scales must be improved (van der Putten et al., 2023; Hannon et al., 2023). Another study used an online survey to explore the moderating effect of gender on the relationship between self-reported camouflaging/masking and anxiety and depression. Researchers found a positive association between masking and mental health issues but no interaction between autistic masking and gender (Hull et al., 2021).
Where do we go from here?
Despite the fact that core traits and descriptions of autism do not include social characteristics, the concept of autism as a “social disorder” has proven pervasive and unyielding. Within this view, the nuanced social difficulties presented by autistic females (without intellectual disabilities) were often overlooked as they did not match the specifically male descriptors used by clinicians. However, contemporary research underscores the fact that autism is a neurodevelopmental condition. Studies reveal sex and gender disparities in various aspects of autism presentation, pathology, and maintenance, and multi-disciplinary frameworks for assessing these disparities have been created (Lai et al., 2021). Researchers therefore assert that, although masking may contribute to diagnostic disparities, gender norms and stereotypes must not be imposed by associating masking/camouflaging with the evolving and expanding definitions of autism (Raymaker et al., 2020). Understanding what sex/gender differences exist in autism trait presentation and neurodevelopment will pave the way for establishing more inclusive descriptions and differential/updated diagnostic criteria and treatments. The following section summarizes contemporary fields of autism research and their potential for taking us forward.
Female autism phenotype
The Female Autism Phenotype theory (FAP) asserts that autistic women and female-presenting individuals possess the same core traits as autistic males but manifest them differently (Kopp & Gillberg, 1992). Although initially published in 1992, FAP has only gained traction in the last decade and has since revealed numerous gender differences in autism presentation. Studies show that autistic women and female-presenting people have better social awareness, are more likely to engage in reciprocal conversation, have more social motivation for friendships, participate in more group activities, use more nonverbal gestures and pragmatic language, have fewer repetitive/restrictive behaviors, and have more friends than autistic men and male-presenting individuals (Hsiao et al., 2013; Hiller et al., 2014; Rynkiewicz et al., 2016; Parish-Morris et al., 2017; Sedgewick et al., 2016; Dean et al., 2017; Wilson et al., 2016).
Neural expression and brain organization
Modern discoveries in brain expression are beginning to characterize neurobiological drivers of sex differences in autism. One study on brain connectivity revealed differential autistic neural expression where females are characterized by patterns of hyper (enhanced)-connectivity and males by patterns of hypo(reduced)-connectivity compared to their neurotypical peers (Alaerts et al., 2016). A similar study revealed that the expression of RORA target genes (essential for neurodevelopment) differs according to sex, where males experience more significant dysregulation of genes associated with autism (Hu et al., 2015). Such findings suggest that RORA expression and brain connectivity are sexually dimorphic (different in females and males), thus invalidating the Extreme Male Brain Theory (Alaerts et al., 2016; Hu et al., 2015).
“… sex hormones work on a gradient, [and] the brain has many secondary sex characteristics. So [the brain] is much more fluid than the primary sex organs. That’s why you do see a lot of variability in terms of gender, as opposed to sex.”
Emily Cassanova, PhD (Interview, 02/21/23)
Gut microbiome – brain axis (GBA)
Trillions of microbial cells (microbiota) make up the gut microbiome (GM) which contains more than 100 times the genetic material of each person’s human genome. Known contributors to GM composition include diet, ethnicity, antibiotics, stress, maternal health during pregnancy, exercise, and psychological and environmental factors (Kim, 2022). The core of the GM resides in the GI tract and plays an integral role in physical and mental health. GI difficulties such as constipation, diarrhea, and abdominal pain commonly co-occur with autism, and many therapies target the GM via dietary and environmental adjustments like Microbiota Transfer Therapy (MTT) (Quigley & Hurley, 2000; Li et al., 2017; Yang et al., 2018; Kang et al., 2017; Nirmalkar et al., 2022). Over the last decade, perceptions of the GM’s capacity and nature have shifted dramatically, unlocking new and exciting avenues of autism understanding and treatment. Specifically, a bidirectional communication pathway called the gut microbiome-brain axis (GBA) has emerged as an influencing factor on metabolism, immunity, behavior, and neurodevelopment. The GBA is established shortly after birth and integrates information from the nervous, endocrine, and immune systems within the communication pathway (Jašarević et al., 2016; Li & Zhou, 2016).
Listen to Dr. Rosa Krajmalnik-Brown discuss exciting treatments in her presentation on Microbiota Transfer Therapy (MTT) in autism
You can also learn about gut health and maintenance in our article on Nutrition and the Gut-Brain Connection
Sex/gender dimorphic GM & GBA
Contemporary studies reveal that the metabolism and circulation of sex hormones (estrogen and androgen) are associated with the GM. The functional capacity and composition of the GM also undergo transitions that mirror periods of dynamic brain development distinctly differentiated by sex (Yoon & Kim, 2021; Jašarević et al., 2016). Further, a study on maternal stress during pregnancy found that stress-induced decreases in vaginal immunity negatively impact the GMs of male children but not females (Kim, 2022). Such findings suggest that GBA maintenance and neurodevelopment are sexually dimorphic and are significantly impacted by changes to the GM. As autism is a neurodevelopmental condition, these findings indicate that sex-based disparities in the structure and function of the GBA partly explain presentation and genetic differences in autistic females and males (Jašarević et al., 2016; Shobeiri et al., 2022).
“Hormone response elements are little segments in the DNA that have the potential to alter gene expression of relevant genes. These guys have presumably been a major source of influence on sexual dimorphism in the primate lineage (human evolution)…Feasibly, these have also been really involved in how the primate lineage has adapted over time, and the kind of sexual dimorphism that you end up seeing throughout the lineage.”
Emily Cassanova, PhD (Interview, 02/21/23)
Beyond the binary
In the past, theories like Extreme Male Brain Theory (EMBT) and Camouflaging exaggerated the idea of a “male” presentation of autism. Against the backdrop of a strictly binary and gender-defined society, such paradigms resonated with cultural norms and traditions. However, contemporary research shows that autistic lived experiences stand in stark contrast to the classical binary understanding of gender. A meta-synthesis exploring the intersection of autism and gender found themes related to: how the autism discourse (i.e., EMBT and masking) restricts gender identities, how gendered autistic identities are positioned within social hierarchies (i.e., as “othered” less acceptable ways of being), and the possibilities of finding spaces for belonging and advocacy (Moore et al., 2022). Autistic females also present with greater gender and sexuality diversity compared to non-autistic females, and many report conflicts between autism and the traditional feminine identity (Bargiela et al., 2016; Pecora et al., 2020). Even further, autistic women and men sometimes display the “typical” brain of the other gender (Sedgewick et al., 2021). Research findings therefore demonstrate that, while autism identity may offer liberation from normative expectations, autism discourse often restricts gender and has, until recently, reinforced classical hierarchies. Modern researchers therefore assert that gender, both statistically and anecdotally, is far more fluid within the autistic population (Moore et al., 2022; Sedgewick et al., 2021; Hall et al., 2020).
New models for a new future
Autism was once understood as a pediatric condition that only affected boys, but we have come a long way since those first descriptions by Kanner and Asperger. We now understand that autism is a lifelong neurodevelopmental condition with heterogeneous (diverse) presentation across all genders. Advancements in understanding and practice allow wider access to autism diagnosis and treatments and therefore continually expand autism descriptions and identities. This integral relationship between “hard” (mathematical) and “soft” (social) science has proven a difficult gap to close for most of autism research history. However, appeals for more holistic and multidisciplinary approaches to investigation and treatment are finally being answered. In alignment with ongoing paradigm shifts in autism understandings, contemporary investigations study models of disability and how they impact policy and practice. The recently proposed Biological Gradient Model (BGM) “integrates scientific theory while avoiding pathology-based concepts and value-laden judgments concerning ‘deficiency’” (Cassanova & Windman, 2021). This model asserts that many phenotypes (presentations) normally pathologized or categorized within the Medical Model need to be considered more as gradients. The BGM is a “hodgepodge” of the best parts of the medical and neurodivergent models. It provides a framework for further examination of the intersection of sex and gender within autism and other neurodevelopmental conditions.
“… it’s just this idea of kind of getting down to the biology of how to describe something, how to describe exactly how this phenotype is coming about. But also with the recognition that a lot of the processes we see functioning within the body are not usually an on-off switch. They tend to be a little bit more of a gradient, or at the very least… may have a threshold effect at some point. But it really does fulfill more of a gradient concept than [whether something] is pathological versus not pathological.”
Emily Cassanova, PhD (Interview, 02/21/23)
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