Sex Differences in Clinical Presentation Among Children with ASD

Background:

The sex ratio in ASD is estimated to be 4:1 and as high as 8:1 in cognitively-able children (Fombonne, 2009; Werling & Geschwind, 2013); however, the literature is less clear regarding sex differences in clinical presentation of children with ASD. The existing literature suggests that girls with ASD have lower IQs and exhibit fewer restrictive and repetitive behaviors (RRBs) than boys (Volkmar, Szatmari & Sparrow, 1993; Hartley & Sikora, 2009). Findings on internalizing and externalizing symptoms have been mixed, and it is unclear whether boys and girls with ASD experience different developmental trajectories. It is important to understand differences between boys and girls with ASD across development in order to improve clinical care.

Objectives: The present study examines sex differences in clinical presentation of children with ASD between 3-17 years of age.

Methods:

The study sample included 396 children ages 3-17 who were diagnosed with ASD and had IQ scores in the average range. All study participants received an Autism Diagnostic Observation Schedule (ADOS) assessment. A subset of participants also received the Vineland Adaptive Behavior Scale (n=289), Child Behavior Checklist (CBCL; n=260), Differential Ability Scale (DAS; n=351), Social Responsiveness Scale (SRS; n=104), and Repetitive Behavior Scale – Revised (RBS; n=207). Sex differences on these measures were examined using independent samples t-tests.

Results:

Independent samples t-tests demonstrated markedly higher general conceptual ability scores on the DAS for boys compared to girls (male M=97.5, female M=91.4, t(351)=2.17, p=0.031), driven primarily by higher spatial ability scores (male M= 97.5, female M=90.9, t(347)=2.75, p=0.006). Boys exhibited more severe ASD symptoms, as assessed by the Calibrated Severity Scale (CSS) of the ADOS (male M=7.59, female M=7.05, t(365)=2.44, p=0.015). Additionally, males exhibited marginally higher scores on the restricted behavior subscale of the RBS (male M=3.46, female M=2.58, t(207)=1.94, p=0.053). On the CBCL, boys under 5 (preschool-aged children) scored significantly higher on the Oppositional Defiant subscale (male M=59.4, female M=52.8, t(26)=2.57, p=0.032) and the ADD/ADHD subscale (male M= 59.0, female M=53.6, t(26)=2.57, p= 0.018). In children ages 9:0-12:0 (school-aged children), girls received higher t-scores on the following subscales of the CBCL: Internalizing Symptoms (male M=59.5, female M=65.3, t(62)=-2.22, p=0.030), Externalizing Symptoms (male M= 53.9, female M= 60.9, t(62)=-2.27, p= 0.027), Anxiety Problems (male M=59.7, female M=65.9, t(61)=-2.61, p=0.012), Anxious/Depressed (male M=59.4, female M=65.4, t(61)=-2.12, p=0.038), and ADD/ADHD (male M=59.7, female M=65.3, t(60)=-2.21, p=0.031). There were no sex-based differences in children ages 13-17 (adolescents).

Conclusions:

Boys displayed more severe autism symptoms in a clinical setting, despite having higher IQs than girls. These more severe symptoms, coupled with increased dysregulation boys exhibited at young ages, may contribute to earlier diagnosis among boys with ASD (Chen, Marvin & Lipkin, 2015). Importantly, school-aged girls exhibited more externalizing and internalizing symptoms than boys. Clinically, these results suggest the importance of symptom monitoring over time, as pre-adolescent girls may experience a period of heightened risk for both internalizing and externalizing symptoms. Future studies should focus on developing effective screening and treatment methods for comorbid psychopathology, particularly for pre-adolescent girls with ASD.