It has been widely established that females are less frequently diagnosed with autism spectrum disorder (ASD) than males. On average, prevalence of ASD is four times higher in males than in females (Baio et al., 2018). This ratio appears to be an inaccurate representation of prevalence by sex/gender. When comparing males and females who are severely impacted by their ASD symptoms, the ratio is closer to 1.33-2 males for every one female (Baio et al., 2018). Determining the ratio of males to females with less severely impactful ASD symptoms has been more complicated. The prevalence ratio has been found to be anywhere between 6-8:1 (Baio et al., 2018) to as high as 16:1 (Fombonne, 2003). Perhaps for this reason, females with ASD had largely been underrepresented in ASD literature. However, a growing body of research has worked to include more females with ASD in studies and specifically look at the female presentation of ASD.
Thus far, the most consistently reported finding on the difference between males and females with ASD is that females have lower IQ scores (i.e., <70) than males (Giarelli et al., 2010). Research on IQ and ASD has looked at discrepancies in Verbal and Nonverbal IQ performance, finding some evidence for better performance in Nonverbal/Performance IQ compared to Verbal IQ (Charman et al., 2011). As is consistent with most of ASD literature, samples are disproportionately male and studies have not devoted time to parsing out gender differences in IQ discrepancies.
A recent study conducted at the Center for Autism and Related Disabilities examined IQ performance of females with ASD, comparing them both to males with ASD and females who were not diagnosed with ASD. The study sample included n = 178 children and adults ranging in age from 2 to 28 years old (M = 10.03, SD = 5.24). There were n = 125 males and n = 53 females in the sample, of which, n = 76 males and n = 20 females received an ASD diagnosis. ASD diagnosis was determined through the use of the Autism Diagnostic Observation Schedule, Second Edition (Lord et al., 2012), and IQ was determined through administration of the Stanford-Binet Intelligence Scales, Fifth Edition (Roid, 2003).
Females with ASD had a mean Full-Scale IQ score of M = 89.25 (SD = 17.11), Nonverbal IQ score of M = 91.45 (SD = 17.54), and Verbal IQ score of M = 88.25 (SD = 19.30). The mean standard score difference between Nonverbal IQ scores and Verbal IQ scores for females with ASD was M = 14.40 (SD = 8.74).
Kristin V. Christodulu, PhD
Cortney Janicki-Menzie
Comparisons between females with ASD and males with ASD showed no significant difference in cognitive ability between groups. Multiple independent samples t-tests revealed no significant differences between ASD-males and ASD-females in regard to Full-Scale IQ score t(94) = .47, p = 64; Nonverbal IQ scores t(94) = .63, p = .53; and Verbal IQ scores t(94) = .26, p = .79. There was no significant difference between ASD-males and ASD-females in mean standard score difference between Nonverbal and Verbal IQ scores t(94) = -1.45, p = .158.
Females with ASD were also compared to n = 33 females who were not diagnosed with ASD. Results from multiple independent samples t-tests showed no significant differences between females with ASD and non-ASD females in regard to Full-Scale IQ score t(51) = -.24, p = .81; Nonverbal IQ scores t(51) = .08, p = .94; and Verbal IQ scores t(51) = -.50, p = .62. There was a significant difference between females with ASD and non-ASD females regarding the mean standard score difference between Nonverbal and Verbal IQ scores t(51) = 2.17, p = .04. Females with ASD had a significantly greater discrepancy between their Nonverbal and Verbal IQ scores than females without ASD.
Results from this project do not support prior research that suggests females with ASD are more cognitively impaired than males with ASD. When females with ASD were compared to non-ASD females, females with ASD had significantly more discrepant Nonverbal and Verbal IQ scores than females without an ASD diagnosis. These discrepancies indicate that females with ASD do not perform uniformly across nonverbal and verbal cognitive tasks in the same way that non-ASD females do. These findings provide new information about the cognitive profile of females with ASD, which had been lacking in previous literature. With these novel findings, we are beginning to better understand females with ASD.
Females with ASD are considered difficult to diagnose (Hull et. al, 2017). However, when females with ASD have co-occurring cognitive impairment (e.g., IQ <70), their developmental concerns may be more apparent. Thus, prior conceptions of females with ASD having lower IQ scores than males with ASD may be a result of a diagnostic bias. In the typically developing literature, females are significantly more social than males (De Goede et al., 2009). Head and colleagues (2014) found a similar trend in children with ASD: females with ASD showed significantly stronger social skills than males with ASD. Females with ASD, however, are significantly behind their typically developing female peers in regard to their social skills. Further complicating the matter, females with ASD have social skills that are on par with typically developing males (Head et al., 2014). Females with ASD have significant deficits in their social skills, but these deficits may not be as striking as males with ASD, since females with ASD are viewed as being just as social as typically developing males.
The social camouflaging theory is emerging in ASD research, and it supports the phenomenon of under-representation of females with ASD. Social camouflaging encompasses multiple coping strategies used to hide one’s social difficulties, such as masking and compensating (Hull et al., 2017). Social camouflaging is seen in both males and females with ASD; however, affected females have higher camouflaging scores than affected males and camouflage their symptoms more often than males (Lai et al., 2017). Societal expectations potentially impact autistic females’ higher rates of camouflaging. Females with autism spectrum disorder feel the need to camouflage more – and by doing so, appear more social – but it is to their own disadvantage. Females adept at camouflaging risk being overlooked and under-diagnosed (Gould & Ashton-Smith, 2013).
While social camouflaging may appear beneficial in the immediate context, it can have long-term detrimental implications. Females – typically developing or with ASD – are at an increased risk of having anxiety and depression, especially during adolescence (Green et al., 1996). People with ASD are also at an increased risk of developing co-occurring psychopathology (Skokauskas & Gallagher, 2012). Females with ASD are an especially vulnerable population given this compounding risk.
An upcoming study at the Center for Autism and Related Disabilities will explore how camouflaging behaviors may impact females with ASD. The study purports that camouflaging has a negative impact on the lives of females with ASD, and it will investigate the use of camouflaging behaviors in women with ASD compared to men with ASD and typically developing women. The study will further explore how camouflaging behaviors may impact the lives of women with ASD, specifically in regard to their mental health, quality of life, and substance use. Understanding of camouflaging is only beginning and further work is needed on outcomes related to these behaviors. Despite growing evidence of gender differences in social presentation and expectations, prevalence of mental health disorders, and quality of life issues, there is a lack of research on outcomes for females with ASD.
Cortney Janicki-Menzie, MA, is a Graduate Assistant at the University at Albany Center for Autism and Related Disabilities. Kristin V. Christodulu, PhD, is Director of the University at Albany Center for Autism and Related Disabilities. For more information about this research, contact Cortney Janicki-Menzie at cjanicki@albany.edu and visit www.albany.edu/autism.
References
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