Clinical Presentation of ASD in Preschool Aged Girls and Boys: Differences That Could Delay Identification of Girls

Background: Autism Spectrum Disorder (ASD) has a male predominance ranging from 4:1 among individuals with Autistic Disorder to 9:1 among individuals with Asperger’s Disorder. Genetic and neurobiological mechanisms are generally thought to explain the higher rates in boys; however, it has been suggested that potential diagnostic bias may to some degree impact the skewed ratio. This may result in girls being under-diagnosed or diagnosed later than boys and failing to access early interventions.  A limited number of studies have explored differences in clinical presentation between preschool aged boys and girls, though numerous studies have found sex differences in cognitive and behavioral profiles for older children with variable results.

Objectives: To examine whether there are sex differences in clinical symptom presentation for preschool aged children diagnosed with ASD.

Methods: The preliminary sample includes 30 children ages 2-4 years (15 males and 15 females) diagnosed with ASD by a multidisciplinary evaluation team. All participants were assessed using the Autism Diagnostic Observation Schedule (ADOS), Childhood Autism Rating Scale, 2^nd Edition (CARS-2), Adaptive Behavior Assessment System, 2^nd Edition (ABAS-II), Behavior Assessment System for Children, 2^nd Edition (BASC-2), and Mullen Scales of Early Learning (Mullen) or Differential Abilities Scales, 2^nd Edition (DAS-II). All female patients diagnosed in the Autism Clinic since November 2008 were included. The male sample was randomly selected from the clinical database of all boys diagnosed during the same time period.   

Results: Preliminary results indicate that boys and girls showed similar levels of functioning on adaptive and cognitive measures, as well as on global scores of clinical symptoms of autism. However, girls scored better than boys on autism instrument items assessing imitation skills (p = .041), relating to people (p = .038), object use (p = .015), and gesturing (p = .012). Boys presented overall with more difficulty regulating activity level (p = .026) and demonstrating appropriate emotional responding (p = .032).

Conclusions: This pilot study suggests that preschool aged girls with ASD differ from their male counterparts in terms of key social skills that could initially mask the severity of their clinical symptoms. Specifically, better ability to use gesturing and imitation, as well as more appropriate use of objects may manifest as more developmentally appropriate social relatedness. Fewer behavioral difficulties in terms of emotional and physical activity regulation may also decrease the severity of their clinical symptom presentation as compared to young boys with ASD. Further research is needed to explore this initial finding, which has implications for potential under-diagnosis of girls and may help explain previous research suggesting that females with high functioning autism/Asperger’s are diagnosed later than males.