Exploring Gender Differences in Core Autism Symptoms

Background:  Autism Spectrum Disorder (ASD) describes a range of complex neurodevelopmental disorders characterized by social and communicative impairments, as well as repetitive behaviors and/or restricted interests.  Given that ASD is about five times more common in males than females (Center for Disease Control and Prevention, 2013), and with evidence of a gender disparity in the clinical presentation of symptoms, many researchers have searched for male/female phenotypic differences.  Few gender differences in ASD symptoms have been found in previous literature, and most findings have been related to IQ.

Objectives:  To investigate the relationship between gender and core ASD symptoms in a large, well-characterized sample.

Methods:  The study sample included 2,254 children and adolescents (1,957 males and 297 females) between the ages of 4 and 17 (M=9.0, SD=42.9), who participated in the Simons Simplex Collection, a multi-site genetic study focusing on simplex families.  Logistic regression was used to examine whether specific variables concerning the core domains of communication, socialization, and repetitive behaviors were significantly related to gender using summary scores from the ADOS and ADI-R. Additionally, predictor variables included Vineland communication scores and ADOS module to measure functional language.  Further regression analyses were then conducted to examine specific behaviors that may be predictive of gender (e.g., specific ADOS and ADI-R subscales).           

Results:  Significant predictors of core autism symptoms included IQ and repetitive behavior scores. No significant gender differences were found in the social and communication domains. There was a significant difference in IQ with males showing higher IQ than females. Further analysis of repetitive behaviors using ADI-R subscales showed males had significantly higher circumscribed interests and unusual preoccupations.  In contrast, females had significantly more midline hand movements and an abnormal response to stimuli.  Post hoc analyses indicated that only those individuals receiving ADOS Module 3 showed a significant difference in repetitive behaviors on the ADOS. Closer examination of Module 3 indicated that males showed a significant difference in a specific code related to greater interest in unusual or highly specific topics and repetitive behaviors. 

Conclusions:  Our study found a significant difference in aspects of behavioral phenotype between males and females. Consistent with past studies, IQ was significantly different with males having a higher average IQ than females. Additionally, repetitive behaviors, specifically circumscribed interests and unusual preoccupations, were more likely in males than females.  Moreover, behaviors including midline hand movements and abnormal response to stimuli were more likely in females.  These results suggest a gender discrepancy in the clinical presentation of core ASD symptoms.