Latent trajectories of early social communication development are associated with autism diagnosis and language outcomes.

Social communication, or a child's ability to interact with others using verbal and nonverbal cues, is a strong predictor of later language development and lifelong outcomes in individuals on the autism spectrum. Interventions that target social communication skills would benefit from careful analysis of the emergence of these skills from their developmental onset. The current study assessed social communication in 801 infants and toddlers using the Communication and Symbolic Behavior Scales (CSBS) at 12, 15, 18, and 24 months of age. Standard social, speech, and symbolic composite scores were modelled in parallel using latent class analysis and growth mixture modeling, to identify distinct classes of children based on social communication trajectories. Class membership was then associated with sex and diagnostic outcome, and associations between 24-month language and social communication trajectory class membership were examined. Secondarily, associations between school age social disability outcomes and early trajectory class membership were examined in a subsample for whom follow-up measures were collected. Two classes of social and symbolic composite trajectories, and 3 classes of speech trajectories were identified. Classes were strongly associated with sex and diagnosis, as well as 24-month language outcomes, controlling for diagnosis and maternal education. Associations between class membership and school age social disability were not robust to controls for diagnosis and maternal education. Across all domains, differences present at 12 months of age persisted or increased through 24 months. Our findings indicate specific trajectories of social communication development which may benefit from interventions targeting social communication skills from around the first birthday. Such interventions would also promote positive development of both receptive and expressive language abilities. Our findings also demonstrate complexity and heterogeneity in development across the breadth of social communication skills, as well as within diagnostic categories. Early assessment of social communication skills-and interventions or educational services aimed at supporting positive development in potentially vulnerable domains-may thus prove beneficial for children before diagnosis, and/or regardless of familial or other likelihood for autism or other developmental delays and disorders.