The Gender Gap in Autism: Where are the Girls?

The Gender Gap in Autism

There has been a significant increase in reported cases of autism over the past decade. Prevalence rates have risen steadily, from one in 150, to one in 110, and now to one in every 54 children (18.5 per 1,000 children aged 8 years). According to the CDC's Autism and Developmental Disabilities Monitoring (ADDM) Network, autism is 4 times more common among boys (1 in 34) than among girls (1 in 144). Statistics also indicate that referrals for evaluation of boys are nearly ten times higher than for girls. Moreover, girls are diagnosed with autism at later ages compared to boys. This gender “gap” raises serious questions because many girls with autism are being overlooked and will not receive the appropriate educational supports and services. 

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 clinical and 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 autism spectrum disorder (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 Girls who have difficulty making sustained eye contact and appear socially withdrawn may also be perceived as “shy,” “naive,” or “sweet” rather than   having the social impairment associated with an autism spectrum disorder.
• 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 depression prior being identified with an autism spectrum disorder.
• 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.
• 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. 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. 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.
• Over reliance on the male model with regard to diagnostic criteria might contribute to a gender “bias” and underdiagnosis of girls. Clinical instruments also tend to exclude symptoms and behaviors that may be more typical of females with ASD. For example, assessment instruments such as the Autism Spectrum Rating Scales (ASRS) and Social Responsiveness Scale (SRS) have generally reported higher mean scores for boys than girls. The lower symptom scores for girls may reflect gender differences and expression of the phenotype. Recent research suggests that certain single test items may be more typical of girls than of boys with ASD, and examining symptom gender differences at the individual level might lead to a better understanding of the gender difference in ASD.
• Apart from biases in reporting or diagnosis, there is significant evidence to suggest that multiple biological factors contribute to the sex differences seen in autism. These include genetic and hormonal differences between males and females that may provide a “protective” mechanism for girls and lead to differences in symptoms and vulnerability to the disorder.

If girls with autism process language and social information differently than boys, then clinical and educational interventions based largely on research with boys may be inappropriate. As a result, autistic girls may receive less than optimal academic and behavioral interventions. If gender specific variations do exist, then the predictive validity of the diagnosis and developmental course may well differ between the sexes. Unfortunately, the consequences of a missed or late diagnosis can result in social isolation, peer rejection, lowered grades, and a greater risk for mental health and behavioral distress such as anxiety and depression during adolescence and adulthood. As a result, there is an urgent need for research to compare girls with autism to typical boys and girls to more fully comprehend the implications of being a girl on the autism spectrum. 

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 “different” by parents, teachers and peers, the possibility of an ASD should be given consideration. Clinicians and school-based professionals should also question the presence of ASD in girls referred for internalizing disorders such as anxiety or depression. 

Best practice assessment and intervention guidelines are available from: A Best Practice Guide to Assessment and Intervention for Autism Spectrum Disorder in Schools (2nd Edition.) and Autism Spectrum Disorder in Children and Adolescents: Evidence-Based Assessment and Intervention in Schools. 

Adapted from Wilkinson, L. A. (2017). A best practice guide to assessment and intervention for autism spectrum disorder in schools (2nd Edition.). London and Philadelphia: Jessica Kingsley Publishers.

Lee A. Wilkinson, PhD, is a licensed and nationally certified school psychologist, and certified cognitive-behavioral therapist. He is author of the award-winning books,  A Best Practice Guide to Assessment and Intervention for Autism and Asperger Syndrome in Schools and Overcoming Anxiety and Depression on the Autism Spectrum: A Self-Help Guide Using CBT. He is also editor of a text in the APA School Psychology Book Series, Autism Spectrum Disorder in Children and Adolescents: Evidence-Based Assessment and Intervention in Schools. His latest book is A Best Practice Guide to Assessment and Intervention for Autism Spectrum Disorder in Schools (2nd Edition)