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Gender Differences during Toddlerhood in Autism Spectrum Disorder: A Community-Based Longitudinal Follow-up Study
Due to the large disparity in prevalence of Autism Spectrum Disorder (ASD) between the genders (3-4 males for every female), differences between diagnosed males and females have long been of interest. The few studies that have investigated gender difference in infants and toddlers focus on differences at one point in time within clinically referred samples or high-risk infant cohorts. It is important to consider children’s developmental trajectories when examining early gender differences in ASD. Further, it is important, where possible, to examine gender differences in samples not subject to the biases inherent in high-risk and clinical cohorts.
Objectives:
The aim in the current study was to examine gender differences in early autism manifestations and cognitive development in a low risk community-ascertained sample of children with ASD from 24 to 48 months of age.
Methods:
Participants were drawn from the Social Attention and Communication Study (SACS; Barbaro & Dissanayake, 2010), where trained Maternal and Child Health nurses undertook developmental surveillance of children in a low-risk community-based setting during their routine child checks. Following identification of early markers of ASD, children were referred for a behavioural and developmental assessment. Sixty-seven participants (46 males; 21 females) who received a diagnosis of ASD at 24-months of age and attended a follow-up assessment 2-years later comprised the study sample. Research reliable clinicians administered the Mullen Scales of Early Learning and Autism Diagnostic Observation Schedule at both time points.
Results:
No significant gender differences were observed on verbal, non-verbal, or overall cognitive ability at either time point. However, there was a significant main effect of time, such that both males and females with ASD improved in their verbal ability, and hence overall cognitive ability, from toddlerhood to preschool. In regards to autism manifestations, no significant differences were found between males and females on overall autism severity or restricted, repetitive behaviours. However, there was a significant gender difference within the social affect scale, such that females with ASD had more severe social-communication impairments compared to males at both time points. In addition, both genders improved significantly across time on overall autism severity, restricted repetitive behaviours, and social affect.
Conclusions:
The only gender difference in our very young community-based sample of children with ASD was in social communication, where females had more social-communication impairments than males. This finding may reflect that toddler females with fewer or different social attention and communication impairments may not be identified during routine developmental surveillance of social attention and communication behaviours, and thus not referred for an ASD assessment prior to 24 months of age. Further, the improvements observed in both genders on verbal ability and autism manifestations from toddlerhood to preschool age supports the rationale of early identification and intervention for children with ASD.