Research review: structural language in autistic spectrum disorder - characteristics and causes.

BACKGROUND: Structural language anomalies or impairments in autistic spectrum disorder (ASD) are theoretically and practically important, although underrecognised as such. This review aims to highlight the ubiquitousness of structural language anomalies and impairments in ASD, and to stimulate investigation of their immediate causes and implications for intervention.
METHOD: Studies of structural language in ASD are reviewed (based on a search of the literature and selected as meeting defined inclusion criteria), and explanatory hypotheses are discussed.
RESULTS: Some individuals with ASD never acquire language. Amongst those who do, language abilities range from clinically normal (ALN) to various degrees of impairment (ALI). Developmental trajectories and individual profiles are diverse, and minority subgroups have been identified. Specifically: language is commonly but not always delayed and delayed early language is always characterised by impaired comprehension and odd utterances, and sometimes by deviant articulation and grammar. Nevertheless, by school age an 'ASD-typical' language profile emerges from group studies, with articulation and syntax least affected, and comprehension, semantics and certain facets of morphology most affected. Thus, even individuals with ALN have poor comprehension relative to expressive language; also semantic-processing anomalies and idiosyncratic word usage. It is argued that impaired socio-emotional-communicative relating, atypical sensory-perceptual processing, and uneven memory/learning abilities may underlie shared language anomalies across the spectrum; and that varying combinations of low nonverbal intelligence, semantic memory impairment and comorbidities including specific language impairment (SLI), hearing impairment, and certain medical syndromes underlie ALI and variation in individual profiles.
CONCLUSIONS: Structural language is universally affected in ASD, due to a complex of shared and unshared causal factors. There is an urgent need for more research especially into the characteristics and causes of clinically significant language impairments.