Bidirectional Relationship Between Language Ability and Internalising/Externalising Behaviour from Early to Late Childhood: Findings from a Chilean Cohort.

Language skills, along with emotional (internalising) and behavioural (externalising) problems, are known to independently influence long-term outcomes. However, the bidirectional relationship between these factors over time, particularly during childhood and early adolescence, remains underexplored. This study used a sample of 3,772 children from the Chilean Longitudinal Survey of Early Childhood to assess bidirectional effects between these domains at ages 2-4, 4-6, and 10-12. Externalising and internalising problems were assessed using the Child Behaviour Checklist, and language ability was measured with the Peabody Picture Vocabulary Test. Structural Equation Modelling, specifically the Random Intercept Cross-Lagged Model, revealed: (a) bidirectional effects between externalising behaviour and language skills, with stronger effects of externalising behaviour on language; (b) externalising symptoms predicted increased internalising symptoms across all periods; (c) internalising symptoms at ages 4-6 predicted lower levels of externalising behaviour at ages 10-12, suggesting a protective role; and (d) gender-specific patterns, with males showing bidirectional effects between externalising symptoms and receptive language, while females showed stronger unidirectional effects of early externalising behaviour on later internalising behaviour. These findings highlight the importance of early monitoring of externalising symptoms and language challenges to mitigate future issues.