An Examination of Cognitive and Adaptive Trends in Children with Autism Spectrum Disorder; A Comparison of Girls and Boys

Background: Despite the difference in prevalence of girls and boys with ASD, little research has investigated variations in developmental patterns between genders (Halladay et al., 2015). Whereas earlier research demonstrated significant gender discrepancies in developmental profiles for children with ASD, more current literature suggests comparable developmental profiles between girls and boys, although these findings lack consensus (Zwaigenbaum et al., 2012). Better understanding of gender differences will result in improved methods of detection and treatment.

Objectives: This study seeks to compare the developmental and adaptive profiles of girls and boys with ASD.

Methods: All children had a confirmed ASD diagnosis and were seen at an autism center, which serves a diverse geographic and socioeconomic population. Assessments included: (1) parent interview (2) assessment of cognitive/developmental abilities using the Mullen Scales of Early Learning or Differential Abilities Scales-2^nd Edition, (3) adaptive assessment using the Vineland Adaptive Behavior Scales, 2^ndEdition, Survey Interview, and (4) ASD assessment using the Autism Diagnostic Observation Schedule. Expressive and receptive language scores on the Mullen were averaged to obtain an overall verbal score. Developmental/cognitive scores were converted to z-scores to compare group means. Subsequently, a verbal domain (VD) was created by combining Mullen overall verbal scores and DAS-II verbal scores. Similarly, Mullen visual reception and DAS-II nonverbal scores were merged to create a nonverbal domain (NVD). Differences in measure values between the genders were considered for the raw values and after adjusting for age via general linear regression. 

Results: Participants included 204 (49 female and 155 male) children between the ages of 21 and 151 months, with girls and boys having comparable mean ages, 49.3 (SD 20.4) and 51 (SD 21.7) months, respectively. Groups were similar with regard to race and ethnicity. There were no differences between genders on the Vineland-II domain or subdomain scores, with the exception of Domestic DLS which was higher in girls when adjusted for age (14.4 (SE 5.9) versus 11.3 (SE 5.0), p= 0.048). Moreover, there were no significant differences between genders on the DAS-II GCA, Verbal, and Spatial domains; however, boys scored significantly higher than girls on the DAS Non-Verbal domain after adjusting for age (83.4 (SE 40.2) versus 70.2 (SE 31.2); p=0.012). There were no significant differences between genders on the Mullen. When DAS-II and Mullen scores were taken together for both genders, there were no significant differences between overall IQ scores or the verbal/language scores. However, similar to the DAS-II data, boys scored higher than girls on the NVD (Z-Score:-1.9 (SD 1.4) versus -2.3 (SD 0.9); p=0.016). 

Conclusions: This study supports the current literature suggesting that there are few differences in adaptive profiles between girls and boys with ASD. However, results of this study indicate that boys’ nonverbal abilities were significantly better than girls. These findings highlight the importance of understanding diagnostic profiles of girls and boys with ASD in order to create the most beneficial treatment plan and intervention for each child. Further research should examine a larger sample size as well as children across different ages and developmental levels.