The loss of acquired language skills in early childhood, which is a distinctive feature of autism, is not linked to later communication development problems, according to a new study.
The research published in The Journal of Child Psychology and Psychiatry found that although a discrepancy in age-equivalent communication skills may persist, this can be expected to be of less practical importance with rising average levels of skills.
Future studies need to account for the significant variability in language trajectories by considering factors beyond developmental regression.
The Pathways in ASD study is a large (N = 421) inception cohort of children with autism spectrum disorder (ASD) who were recruited at the time of diagnosis (between aged two and five years). The sample has been repeatedly assessed to track their developmental, cognitive, and socioemotional functioning across childhood and adolescence.
Children with a diagnosis of cerebral palsy or other neuromotor disorders, identified genetic or chromosomal abnormalities, or significantly impaired vision or hearing were excluded from the study. Caregivers were also required to be verbally proficient in English (or French, in Quebec). The data included in this report were collected at eight assessment points between recruitment (time one) and age 10–11 years (time eight).
Language loss has received the most interest in ASD
The study found that children with language regression walked earlier and attained first words sooner than those without regression. However, both groups attained phrase speech at comparable ages. Those with regression exhibited greater delays in expressive and receptive communication over the follow-up period, although this effect was attenuated when accounting for baseline differences in motor and cognitive ability.
Overall, those with language regression continued to exhibit expressive but not receptive communication delay compared to those without regression. Communication trajectories were heterogeneous to age 10 years, irrespective of regression status.
The authors said that their trajectory analyses highlight the marked variability in communication trajectories in children with autism, both with and without regression.
They added: "Variability in communication outcomes in our sample was associated with some of the factors known to impact rates of language development in the general population, such as income. Future research identifying modifiable factors linked to the external environment could prove especially useful in promoting early language as a protective mechanism for subsequent development.
"Our study focused on language regression because language loss has received the most interest in ASD, but future studies should assess possible loss in multiple domains using more refined measures."