A Comparison of Males and Females Presenting for an ASD Evaluation in Young Childhood

Background: The research on gender differences in ASD symptomatology is inconsistent, yet clinicians often perceive differences in presentation for girls and boys. One large scale study with a wide age range represented found weaker observed social communication and interaction skills for females (Frazier et al., 2014), while another found stronger skills for females, at least on certain ADOS-2 modules (Mussey et al., 2017). Other studies suggest fewer repetitive behaviors in females (Frazier et al., 2014; Mandy et al., 2012). Despite the importance of identifying ASD at an early age, prior research has not specifically focused on gender differences in toddlers and how this may be captured on assessment measures.

Objectives: Evaluate gender differences in autism symptomatology in toddlers, assessed by the ADOS-2, and level of developmental functioning, as assessed by the Mullen.

Methods: The sample consists of 178 males and 44 females between the ages of 14-45 months (M = 29.39 months, SD = 6.5 months) referred based on parent concerns and/or provider recommendations who received an ASD diagnosis. Comprehensive ASD diagnostic evaluations consisted of the Mullen Scales of Early Learning (Mullen), Autism Diagnostic Observation Schedule, Second Edition (ADOS-2), parent-report measures (M-CHAT-R, ASQ-3), and parent interviewing.

Results: Preliminary analyses showed no differences in ADOS-2 module used by gender (Module T = 58%, Module 1 = 36%, Module 2 = 7%). There were no significant differences between the four assessed Mullen domains by gender (Visual Reception: Males M = 31.31, SD = 11.36; Females M = 33.82, SD =11.59, Fine Motor: Males M = 28.45, SD =9.77, Females M = 28.59, SD = 10.18, Receptive Language: Males M = 25.06, SD = 10.4; Females M = 26.36, SD = 10.24, Expressive Language: Males M = 25.86, SD = 9.61; Females M = 26.98, SD = 9.53). Additionally, there were no significant differences in ADOS-2 Social Affect, Repetitive Behaviors, or total scores. At the item level, there was only one trend found with females scoring lower on facial expressions directed to others. Follow-up, exploratory analyses found more differences in toddlers with below average to average Mullen expressive language scores (n = 27 males, 8 females). Girls were found to have significantly lower scores on facial expressions directed to others (t(33)= 3.02, p<.005), quality of social overtures, (t(26) = 2.13, p <.05), and a trend for lower scores on pretend play (t(33) = 1.78, p = .08).

Conclusions: Results are generally consistent with previous research conducted with older individuals finding that girls and boys are more similar than dissimilar. Subtle differences were found for individuals without significant delays in expressive language skills, with girls showing a greater range of facial expressions, increased quality of social overtures, and better pretend play skills; however, this should be interpreted with caution as findings need to be replicated in a larger sample. Although findings from this community-referred sample can be generalized to clinical practice, it is possible that more subtle, higher-functioning children were missed in this sample, particularly considering the delays found developmental functioning for this sample.