Although there has been a dramatic increase in the number of children diagnosed with autism spectrum disorder (ASD) over the past decade, statistics indicate that boys are being referred and identified in far greater numbers than girls (Attwood, 2006; Wagner, 2006). In fact, referrals for evaluation of boys are approximately ten times higher than for girls (Attwood, 2006). Girls are also diagnosed with autism spectrum disorder at later ages relative to boys (Goin-Kochel, Mackintosh, & Meyers, 2006). This gender “gap” raises serious questions because many female students with ASD are being overlooked and will not receive the appropriate educational supports and services (Wilkinson, 2008).
Why are fewer girls being identified? Why do parents of girls experience a delay in receiving a diagnosis? Are there gender differences in the expression of the disorder? Answers to these questions have practical implications in that gender specific variations may have a significant impact on identification practices and the provision of educational services. Although few studies have examined gender differences in the expression of autism spectrum disorders, we do have several tentative explanations for the underdiagnosis and late identification of girls with ASD. They include the following.
- Social communication and pragmatic deficits may not be readily apparent in girls because of a non-externalizing behavioral profile, passivity, and lack of initiative. Girls who have difficulty making sustained eye contact and appear socially withdrawn may also be perceived as “shy,” “naive,” or “sweet” rather than having the social impairment associated with an autism spectrum disorder (Wagner, 2006).
- The diagnosis of another disorder often diverts attention from autism-related symptomatology. In many cases, girls tend to receive unspecified diagnoses such as a learning disability, processing problem, or internalizing disorder. A recent survey of women with Asperger syndrome indicated that most received a diagnosis of anxiety or mood disorder prior being identified with an autism spectrum disorder (Bashe & Kirby, 2005).
- The perseverative and circumscribed interests of girls with autism spectrum disorders may appear to be age-typical. Girls who are not successful in social relationships and developing friendships might create imaginary friends and elaborate doll play that superficially resembles the neurotypical girl (Attwood, 2006).
- Although Students with ASD are more likely to be the target of bullying than typical peers, this may not be recognized in girls due to gender differences in preferred modes of aggression. For example, girls may use covert verbal, social, and psychological forms of aggression while boys tend to rely on confrontational and direct modes of bullying (Besag, 2006). As a result, the more subtle nature of relational and indirect aggression (social exclusion and rejection) used by girls may be taken less seriously than the more obvious, direct aggression exhibited by boys.
- Although girls may appear less symptomatic than boys, the genders do share similar profiles. Research suggests that when IQ is controlled, the main gender difference is a higher frequency of idiosyncratic and unusual visual interests and lower levels of appropriate play in males compared to females (Lord, Schopler, & Nevicki, 1982). As a result, the behavior and educational needs of boys are much more difficult to ignore and are frequently seen by teachers and parents as being more urgent, further contributing to a referral bias (Wilkinson, 2010).
- Over reliance on the male model with regard to diagnostic criteria might contribute to a gender “bias” and underdiagnosis of girls (Kopp & Gillberg, 1992; Nyden et al., 2000). Clinical instruments also tend to exclude symptoms and behaviors that may be more typical of females with ASD.
If girls do process language and social information differently than boys, then clinical and educational interventions based largely on research with boys may be inappropriate Wilkinson, 2008). If gender specific variations do exist, then the predictive validity of the diagnosis and developmental course may well differ between the sexes. Meanwhile, educators and school personnel should question the presence of an ASD in girls referred for internalizing disorders such as anxiety or depression. Best practice recommends that when a girl presents with a combination of social immaturity, restricted interests, limited eye gaze, repetitive behaviors, social isolation, and is viewed as “unusual” or “odd” by parents, teachers and peers, the possibility of an ASD should be given consideration (Wagner, 2006; Wilkinson, 2010)
Lee A. Wilkinson, PhD is the author of the award-winning book, A Best Practice Guide to Assessment and Intervention for Autism and Asperger Syndrome in Schools, published by Jessica Kingsley Publishers.
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