Sex differences in minimally verbal children and adolescents with autism
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The prevalence of autism spectrum disorder (ASD) is higher in males than females. Previous research has uncovered a female protective effect in which females have a higher threshold for genetic abnormality before being affected by ASD. Because this also suggests that females with ASD will have more severe symptoms, sex differences in symptoms could provide support for this theory. The present study investigated differences in autistic symptoms and characteristics in 20 boys and 5 girls aged 5-21 who represent a unique subset of the autistic population: minimally verbal individuals. The participants, the majority of whom failed to develop language beyond phrase speech, completed a variety of assessments at Boston University’s Center for Autism Research Excellence (CARE). The present study was a secondary analysis of cross-sectional data from two previous studies conducted between May 2012 and July 2014 at CARE. Sex differences in overall symptoms and the domains of nonverbal cognitive ability, social functioning, repetitive and maladaptive behavior, and structural and pragmatic language from standardized tests and language samples were examined. Language sample videos and the associated transcriptions were coded based on whether the child directed his/her speech to other people and the intention behind their language: whether they used speech for the purpose of behavior regulation, joint attention, social interaction, or an unknown purpose. There were no significant sex differences found in any of the measures and no effect of sex when controlling for age and IQ. There was a significant effect of IQ found for maladaptive behavior, social functioning, language level, directed speech, and speech used for joint attention. There was also a significant effect of age on language ability and directed speech. These findings partially conflict with those of previous literature in verbal autistic individuals, suggesting that minimally verbal individuals have distinct symptomatic profiles. The finding of no sex differences in autism symptoms suggests that if a female protective effect exists, it does not manifest in more severe symptoms in minimally verbal females. Therefore, this study contributes to the knowledge of sex differences in autism by characterizing the symptomatic profiles of this subgroup.