Is Early Verbal and Nonverbal Language Gain Related to Autism Spectrum Disorder’ Symptomatology in Infants at Risk?
Objectives: We first aim to define distinct developmental trajectories for early language and gesture acquisition in siblings at HR for ASD and in LR children using an extensive parent-report questionnaire. Our second purpose is to identify early predictors and clinical and cognitive outcomes related to the derived trajectory groups based on verbal and nonverbal communication gains.
Methods: We used Group Based Trajectory Models (GBTM) to derive early communication trajectory groups. Data for language (expressive and receptive) and gesture acquisition were collected with the MacArthur Communicative Development Inventory-Infant Form (M-CDI) at 9, 12, 15, 18, 21 and 24 months of age. The sample was composed of 660 HR and LR infants (482 HR siblings, 361 males in the total sample). Clinical and cognitive measures were also collected before and after this period (at 6 and 36 months respectively). Predictors and outcomes were further examined according to the trajectory groups derived for each of the three measures. Finally, membership in each trajectory groups was analyzed with regard to the diagnostic outcome at 36 months.
Results: Analysis revealed three distinctive trajectory groups for the receptive language and gesture gain measures, and two groups for the expressive language acquisition measure. Pairwise comparisons between trajectory groups for the estimates of quadratic slope revealed significant differences for all comparisons (all p<.001) except for slopes 1 and 2 for gestures (p=.14). Intercepts for verbal expression and gestures did not differ significantly between trajectories (all p>.17), except for receptive language (all p<0.01). For each measure (expressive language, receptive language, and gestures), assigned trajectory groups were strongly related to clinical and cognitive outcomes. Children with an ASD diagnosis were less likely to be in the trajectory groups with the fastest language/gesture acquisition for all three measures. Clinical and cognitive measures at 6 months predicted trajectory group membership for receptive language and gesture gains. Global motor functioning was the only predictor for expressive language trajectory membership.
Conclusions: Our results confirm substantial variability in communication gains in the early development of both HR and LR infants. The results also suggest that this variability predicts further ASD symptomatology and is related to very early risk factors. Beyond communication-related behavioral features, predictors include motor skills and cognitive functioning. The current study has clinical implications in pointing out relevant language-related targets for early intervention.