Chapter 4. Do autism spectrum disorders and specific language impairment have a shared aetiology?
There has been considerable debate in the literature regarding the aetiological relationship between Autism Spectrum Disorder (ASD) and Specific Language Impairment (SLI). While some authors have suggested that similarities in the language phenotypes of the conditions represent a theoretically significant aetiological overlap, others argue that the overlap is superficial and not reflective of shared causes. This chapter reviews the published literature with regard to the hypothesised aetiological relationship between ASD and SLI. Specifically, we review studies investigating behavioural and linguistic overlap between ASD and SLI, before considering results of neurological and molecular genetic studies. While several studies have highlighted phenotypic similarities between ASD and SLI, there is a considerable degree of inconsistency throughout the literature and current evidence does not support aetiological overlap. Important avenues for future research are investigating whether there are shared neurological and genetic pathways contributing to ASD and SLI.