Developmental disorders in girls: Focus on autism spectrum disorders

Autism spectrum disorders Autism spectrum disorders (ASD) are neurodevelopmental disorders classically characterized by qualitative impairments in reciprocal social interaction, communication, restricted interests and repetitive and stereotyped patterns of behaviors. The term autism spectrum disorder, only recently included in the Diagnostic and Statistical Manual (DSM-5), includes conditions classified as childhood autism, Asperger syndrome and other conditions classified as pervasive developmental disorders in DSM-IV and the International Classification of Diseases (ICD-10). In this chapter, we use the term autism interchangeably with ASD. The reported prevalence of ASD has markedly increased over the past few decades. Fewer than 1 in 2000 children were estimated to have these disorders in the 1980s although recent population-based studies report a prevalence of 1% or greater of the child (Baird et al., 2006; Centers for Disease Control and Prevention, 2012; Idring et al., 2012; Kim et al., 2011) and adult (Brugha et al., 2011) population. ASDs appear to be underrepresented in females in clinical as well as epidemiological studies. This gender bias has been evident since the earliest descriptions of autism (Asperger, 1944; Kanner, 1943). The male:female ratio in the various studies ranges from 2:1 to 9:1 (Baird et al., 2006; Baron-Cohen et al., 2009; Brugha et al., 2011; Idring et al., 2012; Kim et al., 2011; Lord et al., 1982; Mattila et al., 2011; Wing, 1981). The studies also point to the possibility that women and girls with autism exhibit relatively higher rates of coexisting intellectual disability (ID) than men and boys with autism (Lord et al., 1982; Volkmar et al., 1993; Wing, 1981). The differences in the sex ratios observed across studies may be linked to differing methods of case-finding, diagnostic methods and definition of ASD; varying levels of ASD severity; and different proportions of individuals with co-occurring intellectual disability. However, a male preponderance of ASD is a consistent finding across studies and fits with the male preponderance in all neurodevelopmental disorders. Despite much research, the reason(s) why ASD may be relatively underrepresented in females are not yet fully understood. In this chapter, we present an overview of the various possibilities that have been proposed to explain this phenomenon, and their implications for women with autism.