Are African American Girls with ASD More or Less Impaired Than Boys? It May be All about IQ

Background:

The field of autism has a tremendous need to better understand sex differences and the profiles of girls with autism spectrum disorders (ASD). To date, the largest phenotypic study investigating sex differences found that girls with ASD had significantly lower cognitive and adaptive skills than boys with ASD, and significantly more externalizing behaviors (Frazier, Georgiades, Bishop, & Hardan, 2014). Though there were more than 2000 individuals in the study, the sample was predominantly high functioning and roughly 75% White/non-Hispanic. Few studies have directly investigated sex differences within and across racial groups.

Objectives:

This study investigates sex differences in phenotyptic presentations in a sample of African American individuals with autism, including differences in cognition, autism symptomatology, and adaptive behavior.

Methods:

Participants included 97 African American individuals with autism (26 female and 71 male) ages 3-18 years (mean=7.78 years, SD=3.79). Measures included the Differential Ability Scales, 2^nd Edition (DAS-II); the Mullen Scales of Early Learning, the Autism Diagnostic Observation Schedule, 2^nd Edition (ADOS-2); the Autism Diagnostic Interview, Revised (ADI-R), and the Vineland Adaptive Behavior Scales, 2^nd Edition, Survey Form (Vineland-II).

Results:

Fifty-five percent of the sample had cognitive scores below 70 and 50% of mothers had a maternal education below college level. ANOVA analyses revealed no significant differences on IQ, ADOS, ADI-R, or Vineland-II scores between males and females for the full sample. However, when the sample was grouped by High IQ (IQ>70) and Low IQ (IQ<70), significant differences emerged. For the Low IQ group, there was a trend for girls having significantly lower verbal IQ scores [F(1,38)=3.32, p=.076], with a mean Verbal IQ of 36.10 (SD=9.63) compared to 45.40 (SD=15.07) for boys. Girls also had significantly lower Vineland Socialization scores (Mean=58.00, SD=6.25) than boys (Mean=65.32, SD=11.18) F(1,51)=4.66, p<.05. For the High IQ group, there were no significant differences in cognition, but girls had significantly higher Vineland Socialization score than boys (Girls Mean=75.46, SD=8.24; Boys Mean=67.00, SD=11.07) F(1,40)=6.06, p<.05. No significant differences were observed across samples in levels of autism symptomatology on the ADOS or ADI-R. However, regardless of sex, the Low IQ group had significantly higher ADOS CSS scores than the High IQ group [F(1,84)=4.35, p<.05].

Conclusions:

Results from the overall sample of African American school-aged individuals with ASD revealed no significant sex differences in cognition, autism symptomatology, or adaptive behavior. Sex differences emerged when the sample was split by cognitive level. Girls with ASD with cognitive impairment had significantly lower verbal abilities and adaptive socialization scores than boys, but girls without cognitive impairment had significantly higher adaptive socialization scores than boys – contrary to prior research. Of note, 58% of boys and 46% of girls fell into the Low IQ group, highlighting the discrepancies in percent of cognitive impairment in our African American sample compared to national estimates (e.g., CDC, 2012 prevalence of 38%). These findings suggest that cognition could play a stronger role in potential sex differences in ASD compared to, for example, symptom severity in African American individuals. Limitations and implications for further research will be discussed.