Gender Differences in ASD through a Developmental PRISM

Background: In both Kanner’s and Asperger’s original samples, males were dominant: eight of the eleven children Kanner described and all four of Asperger’s children were male. Over the past two decades, a trend towards decreasing male-predominance has emerged (Jensen, Steinhausen, & Lauritsen, 2014), with recent epidemiological studies showing a 3:1 male-female ratio (Werling & Gerschwind, 2015). Females with autism may be under-identified and underrepresented, resulting in a possible male-biased understanding of autism. The present research is an attempt to understand ASD characteristics in young females, and to specify cognitive profiles and ASD symptomatology at the time of diagnosis and three years later.

Objectives: This longitudinal study compares cognitive and ASD profiles of boys and girls in their third year of life and again at age six in order to address gender similarities and differences over time.

Methods: Sixteen girls and 50 boys with suspected ASD were assessed before age three (girls’ ages in months: M = 26.377, SD = 3.224; boys’ ages in months; M = 27.127, SD = 2.873) and again at around age six (girls: M = 69.382, SD = 4.538; boys: M = 72.452, SD = 4.296). At first assessment, before age three, cognitive abilities of all participants were assessed with the Mullen Scales of Early Development and the ASD profile was assessed with the ADOS toddler module. Cognitive abilities around age 6 were assessed with either the Wechsler Preschool and Primary Scales of Intelligence or the Mullen Scales of Early Development, and ASD profiles with the appropriate ADOS Module.

Results: Although there were no significant differences between the males and females at the initial assessment (girls’ DQ: M = 66.21, SD = 12.74; boys’ DQ: M = 62.968, SD = 14.673), a difference emerged around the age of six, with the girls’ IQ being significantly lower than that of the boys (girls: M = 77.987, SD = 22.158; boys: M = 103.442, SD = 31.945). Similarly, differences emerged in autism symptomatology around age six, although no significant differences appeared before age three. By age six, the ADOS profiles of girls revealed fewer social-affective symptoms and fewer restricted and repetitive behaviors.

Conclusions: By age six, the gender differences evident in cognitive profiles and ASD symptomatology are similar to those documented in previous research despite the fact that no gender differences emerged around age three. Incorporating language, behavioral and cognitive factors in the longitudinal study of gender in ASD may shed light on diverging developmental trajectories in males and females with ASD. In order to understand ASD it is important to recognize the implications of a possible male bias, which may make it difficult to identify females with ASD, particularly at an early age.