Temporal Pattern of Co-Development of Internalizing and Externalizing Problem Behaviors: An Application of Bivariate Mixed-Effects Models

Background: Although previous research has shown that internalizing and externalizing behavior problems often co-occur, the relationship between the developmental trajectories of these two types of behavior problems is understudied. The co-occurring evolutions of developmental trajectories of two behaviors has two components: 1) the correlation between the slopes of two behavior profiles (termed the association of the evolutions); and 2) the marginal correlation of two development trajectory profiles, which is the development of correlation between internalizing and externalizing behavior over time (termed the evolution of the association). The association of the evolutions and the evolution of the association have not been fully explored in the context of the development of internalizing and externalizing behavior problems among kindergarteners in the United States. Methods: The random-effects approach for joint modeling of multivariate longitudinal profiles was used to evaluate the co-development and its temporal pattern of internalizing and externalizing behavior problems on a nationally representative sample of 9791 kindergarteners from the Early Childhood Longitudinal Study-Kindergarten Class of 1998-99 (ECLS-K). Results: here was a moderate positive association between the evolutions of the two behavior problems with correlation coefficient of 0.319. The evolution of association between the two behaviors was increasing over time with the correlation coefficient from 0.195 at the Fall of kindergarten to 0.291 by the time of fifth grade in general. Race and age groups act differently on the evolution of association. The associations were getting stronger for the Asian group and older groups than their peer groups. Conclusion: This investigation of the association of evolutions and the evolution of association between the internalizing and externalizing behaviors show that the two problem behaviors reciprocally reinforce each other and lead to increases in the other in a moderate strength and the strength is increasing over time.