Sex Differences in Internalizing Symptoms in Young Children with ASD

Background:  Few studies have examined sex differences in co-occurring behavioral and emotional problems among children with Autism Spectrum Disorder (ASD) and existing findings are mixed with some research suggesting increased affective symptoms in girls and externalizing symptoms in boys. 

Objectives: To evaluate sex differences in co-occurring behavioral and emotional problems in a large clinical sample of children referred for and diagnosed with ASD. 

Methods: 18 ATN sites, data collected from 2007 to 2013, on all subjects age 1.5 to 5.11 years with complete CBCL (version 1.5 to 5) and ADOS data (N=2941; mean age: 3.9 years, SD=1.08). Based on the T-scores, 5 narrow- and 3 broad-band CBCL scores were classified in 3 levels (Normal range: <60;  Borderline: >=60 and <70; Clinical: >=70). CBCL data were also examined as continuous scores. Algorithm scores and calibrated severity ADOS scores were available as well as Vineland Adaptive Behavior Scales (VABS) on all participants.  

Results: There were 2,446 boys (83.2%), 495 girls (16.8%), and no difference between sexes for mean age at assessment, ATN site, or ethnicity (Hispanic or not). There was a slight overrepresentation of girls among Black and “Other” race families (p=.05) and parents with higher education (p=.03).

No significant difference was found between sexes in levels of Somatic Complaints, Withdrawal, Attentional problems, Aggressive behaviors, Externalizing and Total CBCL scores (all p’s>.15). Higher proportions of girls scored in the clinical range for Anxiety problems (12.5% vs 7.7%; p=0.001) and Internalizing problems (32.3% vs 26.3%; p=.024). Similar results were obtained using continuous scores with girls scoring higher than boys on mean Anxiety T-scores and Internalizing T-scores (respectively: 57.8 vs 56.6, p=.01; 64.4 vs 63.1, p=.01); girls also showed higher scores on the Withdrawal scale (72.0 vs 70.9, p=.03) and on the Total score (64.8 vs 63.7, p=.04).

Further girls-only analyses on Anxiety and Internalizing scores indicated girls in the two older age groups (<3 y; 3 to 4.5 y; over 4.5 y) had slightly higher levels of anxiety, and significantly higher levels of Internalizing problems (chi-2=12.4, 4 df; p=.013). One-way ANOVAs (3 levels of anxiety: Normal, Borderline, Clinical) were used to compare means on 5 VABS standardized scores and 3 ADOS calibrated severity scores and yielded no significant difference for levels of Anxiety problems. In all VABS analyses, girls with Clinical levels of Internalizing problems scored lower (more impairment in Communication, Socialization, Daily Living Skills, Motor Skills and Adaptive Behavior Composite) than girls in the Normal range, with girls with Borderline levels scoring in-between the other 2 groups. For the ADOS calibrated severity scores, a trend was found for girls in the Normal range of Internalizing problems to have slightly less severe scores on the Repetitive and Restricted Behavior calibrated severity scale (p=.058).

Conclusions: Overall, findings suggest girls with ASD are more likely than boys to demonstrate anxiety and internalizing problem behaviors; however, there were no sex differences found in regards to externalizing problem behaviors. Follow-up analyses will examine affective and behavioral differences by gender among older children with ASD.