Communication and social deficits in relatives of individuals with DLD and relatives of individuals with ASD
Both individuals with Autism Spectrum Disorder (ASD) and Specific Language Impairments (SLI) are known to have language and communication deficits. A growing body of research is interested in the similarities in their etiology and the heritability of impairments in SLI and ASD through family studies.
This study investigates both communication and social deficits in relatives of SLI probands and compares them with the relatives of probands with ASD and Down Syndrome (DS). The inclusion of DS provided an opportunity for comparisons of SLI and ASD with DS, a non-heritable disorder. The overall aim of the study is to develop our understanding of how SLI relates to autism spectrum disorder both in terms of heritability and etiology.
*Proband - a person serving as the starting point for the genetic study of a family.
Relatives of probands with SLI had higher rates of communication deficits and lower rates of social deficits, whilst relatives of probands with ASD had higher rates of social deficits and lower rates of communication deficits.
Interestingly, relatives of probands with SLI accompanied by autistic symptomatology were found to have similar rates of affectedness of social deficits as relatives of probands with ASD. This provides evidence for the likely heritability of social deficits in some families with a proband with SLI and further suggests that heritability of social deficits is more likely in families where there is a proband who has additional ASD symptomatology.
In terms of the debate regarding whether SLI and ASD have similar or distinct etiologies to their communication deficits, these findings support the view of likely different etiologies for these disorders.
Similar levels of social deficits were found in relatives of probands with SLI with ASD and probands with ASD.
There was evidence to suggest that social deficits are heritable in ASD but are less likely to be so in SLI.