Developmental path between language and autistic‐like impairments: a twin study

Abstract

Autism spectrum disorders (ASDs) are diagnosed when individuals show impairments in three behavioural domains: communication, social interactions, and repetitive, restrictive behaviours and interests (RRBIs). Recent data suggest that these three sets of behaviours are genetically heterogeneous. Early language delay is strongly associated with ASD, but the basis for this association and the relationship with individual sub-domains of ASD has not been systematically investigated. In the present study, data came from a population-based twin sample with language development data at 2-4 years, measured by the MacArthur Communicative Development Inventory (MCDI), and data at 8 years using the Childhood Asperger Syndrome Test (CAST). For the total CAST and the three subscales at 8 years, approximately 300 same-sex twin pairs were selected as showing extreme autistic-like traits (ALTs), defined here as pairs in which at least one member of the twin pair scored in the highest 5% of the distribution. Phenotypic analyses indicated that children showing extreme social and communication ALTs (but not the RRBI subscale) at 8 years were below average in language development at 2-4 years. A regression model for selected twin data suggested that genetic influences account for this overlap, but that these effects are only in part mediated by genes that are shared between language and extreme autistic traits.

Relationship Between Symptom Domains in Autism Spectrum Disorders: A Population Based Twin Study

“…A new aspect of the present study was inclusion of a language delay score. The findings reported here are consistent with previous work related to language delay which has shown that more general early vocabulary and grammar abilities show phenotypic and genetic relationships with later social and communication impairments and traits, but not RRBIs (Dworzynski et al 2007(Dworzynski et al , 2008. This highlights the fact that a separation of domains can shed light on the aetiological relationships with other traits or abilities.…”

Language in autism and specific language impairment: Where are the links?

“…Adopting a different approach, Dworzynski et al (2008) explored genetic links between early language difficulties and later autistic-like traits in a population-based twin sample. The language abilities of all twin-pairs in the Twins Early Development Study (Oliver & Plomin, 2007) were assessed by parent-completed questionnaires concerning expressive vocabulary and grammar, at ages 2, 3, and 4 years.…”

Is the child ‘father of the Man’? Evaluating the stability of genetic influences across development

“…Longitudinal twin studies can also explore genetic stability and change on the comorbidity between two traits or disorders across development. Recent examples of this are studies on the longitudinal etiological relationship between autistic traits and anxiety‐related behaviors (Hallett, Ronald, Rijsdijk & Happé, 2010) and the longitudinal etiological relationship between autistic traits, and intelligence and verbal ability (Dworzynski, Ronald, Hayiou‐Thomas,, McEwen, Happé, Bolton & Plomin, 2008; Hoekstra, Happé, Baron‐Cohen & Ronald, 2010). As such, these studies demonstrate to what degree the same genetic influences on one trait or disorder at an earlier age are also involved in a related trait or disorder at a later age.…”