Measuring the Impact of Genetic and Environmental Risk and Protective Factors on Speech, Language, and Communication Development-Evidence from Australia.

Speech and language acquisition is one of the key development indicators of optimal literacy development in infancy and early childhood. Over the last decade there has been increasing interest in the development of theoretical frameworks which underpin the underlying complexity of a child's language developmental landscapes. This longitudinal study aims to measure the impact of genetic and environmental risk and protective factors on speech, language, and communication development (SLCN) among 5000 infants in Australia. Using robust panel fixed-effects models, the results demonstrate that there are clear and consistent effects of protective factors and SLCN associated with the infant's family [coefficient (SD) = 0.153, 95% standard error (SE) = 8.76], the in utero environment [coefficient (SD) = 0.055, standard error (SE) = 3.29] and early infant health [coefficient (SD) = 0.074, standard error (SE) = 5.28]. The impact of family and in utero health is dominant at aged 2 to 3 years (relative to 0 to 1 years) across the domains of language and communication and more dominant from birth to 1 years for speech acquisition. In contrast, the evidence for the impact of genetics on SLCN acquisition in infancy, is less clear. The evidence from this study can be used to inform intervention policies.