Preadolescent psychosocial maladjustment in children who exhibited different developmental patterns of co-occurring externalizing behaviors during the preschool years.

The co-occurrence of externalizing behaviors (EBs) in school-aged children is associated with long-term homotypic (similar) and heterotypic (diverse) psychosocial difficulties. It is unknown whether this developmental process begins with the first manifestations of EBs in the early preschool years. This population-based cohort study examined psychosocial maladjustment at ages 10-12-including externalizing problems, addictive behaviors, internalizing problems, and socialization difficulties-among children who followed distinct patterns of single or co-occurring EBs across the preschool years. EBs included parent-rated hyperactivity-impulsivity, noncompliance, and physical aggression. Six high-trajectory classes, identified with latent growth modeling, were used as longitudinal indicators of EBs and compared to a reference class of children with low or moderate trajectories across all EBs, controlling for internalizing problems and other confounders. Results indicated that all trajectories characterized by high levels of single or co-occurring EBs showed homotypic continuity, and most exhibited heterotypic continuity, at ages 10-12. Preschoolers with a high co-occurrence pattern encompassing all three EBs showed the poorest psychosocial adjustment across all 14 outcomes in the four maladjustment domains. Differences between the other trajectories with high levels of single-EB and co-occurring EBs, relative to the reference class, were more mixed. Results suggest that high and stable levels of a single EB or co-occurring EBs in preschool are associated with significant homotypic and heterotypic continuity into preadolescence. They underscore the importance of early manifestations of EBs and highlight that the multiple co-occurring EBs observed in preadolescents originate from similar patterns observable during the preschool years. (PsycInfo Database Record (c) 2026 APA, all rights reserved).