Early trajectories and moderators of autistic language phenotypes: a longitudinal study in preschoolers

Abstract Language difficulties in autism emerge early and significantly impact social functioning and quality of life. Despite their wide heterogeneity, autistic language abilities can be parsed into three distinct phenotypes. Language Unimpaired (LU) exhibit near-typical verbal performance, Language Impaired (LI) show significant alterations in language structure, and Minimally Verbal (MV) display limited verbal abilities. However, little is known about the early trajectories and moderators specific to each phenotype. Here, we used a longitudinal sample of 286 preschoolers with autism and 85 typically developing (aged 1.5–5.7 y.o.), yielding 1164 visits. Our cluster analysis replicated the three well-established autistic language phenotypes (LU, n = 86; LI, n = 85; MV, n = 44) and revealed their specific early trajectories. At age 2.5, LU could be identified by their higher general cognition compared to the other phenotypes, while MV were characterized by a major delay in non-verbal cognition. Moreover, the presence of early stereotyped language specifically predicted LU’s later verbal performance, while LI language outcome was improved by early behavioral intervention. In conclusion, we provided a fine-grained description of early trajectories and moderators of autistic language phenotypes in a longitudinal sample exposed to French language, paving the way toward personalized medicine to autistic language difficulties. *The authors would like to note that Kenza Latrèche and Michel Godel contributed equally to the study.