Sex Differences in CARS Scores for Toddlers with Autism Spectrum Disorders
Autism Spectrum Disorder (ASD) is four times more prevalent in boys than girls (CDC 2018). Girls may display a different symptom profile than boys, which may impact diagnosis rates; however, previous studies report conflicting results on sex differences in ASD symptoms. Some studies report no significant differences between sexes (Carter et al., 2007), while others report more stereotyped behavior in boys (Hartley & Sikora, 2009) and greater social communication impairments in girls (Lawson et al., 2018). Studies examining sex differences in total and item level scores on ASD diagnostic measures present similar contradictions (Beggiato et al., 2017; Pilowsky et al., 1998 Rynkeiwicz et al., 2016; Tillman et al., 2018). Given these inconsistent results and that participants in most of these studies are older children and adults, more research is needed to determine sex differences in ASD symptoms among toddlers and how these differences impact the utility of diagnostic tools.
To investigate sex differences in scores on the Childhood Autism Rating Scale (CARS) to examine the utility of the CARS for toddler-aged boys and girls. Specifically, based on prior literature, to test the hypothesis that male and female toddlers receive similar scores on overall severity, emotional reactivity, and stereotyped behaviors, but female toddlers exhibit more impairment in social communication.
Participants for this study were part of a multi-site early detection study (Robins et al. 2014). Parents completed the Modified Checklist for Autism in Toddlers, Revised with Follow-Up (M-CHAT-R) at their child’s 18- or 24-month checkup and were offered a diagnostic evaluation if the child screened at risk after follow-up. This sample includes 323 participants who completed the evaluation between the ages of 17 and 27 months and met ICD-10 criteria for Childhood or Atypical Autism. There were no significant differences between sexes in age (t(321)=0.308, p>.05) or cognitive ability (t(321)=-0.671, p>.05). The CARS is a 15-item observation-based rating scale that yields a total score reflecting ASD symptom severity (Schopler et al., 1980). CARS items were divided into three factors (social communication, emotional reactivity, and stereotyped behaviors and sensory sensitivities) based on a factor analysis completed by Moulton et al. (2016). Factor scores were calculated by averaging the scores of all items included in a factor.
No significant differences were found between boys and girls on total severity scores, factor scores, or individual item scores (Table 2).
Results support the hypothesis that male and female toddlers score similarly on overall severity, emotional reactivity, and stereotyped behaviors. Results do not support the assertion that female toddlers score higher on items assessing social communication. This suggests that the CARS is a valid diagnostic measure for both male and female toddlers and supports previous findings that show little to no sex differences in ASD core symptoms (Carter et al., 2007). Future studies should continue to compare the symptoms reported for male and female toddlers with ASD to determine any sex differences in symptom profiles and determine the utility of diagnostic measures across sexes.