It is well established that autism spectrum disorder (ASD) is more prevalent in males than females, with 1:42 boys and 1:189 girls meeting ASD criteria (Home, C.D.C., 2014). Despite this being a topic of great interest (see recent special issue in Molecular Autism, vol. 6), the mechanisms underlying sex differences in the prevalence of autism as well as in other childhood-onset psychiatric conditions are still poorly understood (Rutter, Caspi & Moffitt, 2003). In order to characterise sex differences in infant markers previously shown to predict emerging symptoms of autism, we take a developmental approach using a prospective sample of infants at high risk for ASD. The aim of the current paper is to assess whether sex differences are apparent in known early autism markers or in the relationships between early markers and later autistic traits. According to a prominent hypothesis - the differential liability model - boys are more susceptible than girls because they are subject to a greater number of boy-specific risk factors, or because girls benefit from specific protective factors. The nature of these factors remains unknown. Language has often been suggested as protective factor, since girls lead in language skills from early in development (e.g., Eriksson et al., 2012). However, evidence suggests that autistic girls with better language also have better cognitive and adaptive skills, which is not consistent with the idea of protection (e.g., Howe et al., 2015; Lai et al., 2011). Indirect evidence for girl-specific protective factors comes from studies showing that a higher load of genetic/phenotypic risk is needed for girls to eventually express autistic traits (Werling & Geschwind, 2013). For example, siblings of girls with autism show a higher incidence of autism than siblings of boys with autism (Werling & Geschwind, 2015, although see Pickles et al., 2000 and Messinger et al., 2015 for absence of evidence). Studies of phenotypic differences between males and females with autism may achieve the aim of identifying sex specific risk or protective mechanisms. One commonly
It is well established that autism spectrum disorder (ASD) is more prevalent in males than females, with 1:42 boys and 1:189 girls meeting ASD criteria (Home, C.D.C., 2014). Despite this being a topic of great interest (see recent special issue in Molecular Autism, vol. 6), the mechanisms underlying sex differences in the prevalence of autism as well as in other childhood-onset psychiatric conditions are still poorly understood (Rutter, Caspi & Moffitt, 2003). In order to characterise sex differences in infant markers previously shown to predict emerging symptoms of autism, we take a developmental approach using a prospective sample of infants at high risk for ASD. The aim of the current paper is to assess whether sex differences are apparent in known early autism markers or in the relationships between early markers and later autistic traits. According to a prominent hypothesis - the differential liability model - boys are more susceptible than girls because they are subject to a greater number of boy-specific risk factors, or because girls benefit from specific protective factors. The nature of these factors remains unknown. Language has often been suggested as protective factor, since girls lead in language skills from early in development (e.g., Eriksson et al., 2012). However, evidence suggests that autistic girls with better language also have better cognitive and adaptive skills, which is not consistent with the idea of protection (e.g., Howe et al., 2015; Lai et al., 2011). Indirect evidence for girl-specific protective factors comes from studies showing that a higher load of genetic/phenotypic risk is needed for girls to eventually express autistic traits (Werling & Geschwind, 2013). For example, siblings of girls with autism show a higher incidence of autism than siblings of boys with autism (Werling & Geschwind, 2015, although see Pickles et al., 2000 and Messinger et al., 2015 for absence of evidence). Studies of phenotypic differences between males and females with autism may achieve the aim of identifying sex specific risk or protective mechanisms. One commonly
SexDifferences_ForSubmission.docx