Longitudinal Association and Mediating Mechanism Between Externalizing and Internalizing Problems Among Children: A Within-Person Analysis.

Objective: In this multi-informant, 3-year longitudinal study, the bidirectional relations between externalizing and internalizing problems were investigated, along with whether peer victimization and academic achievement mediated their relations after separating between-person effects from within-person effects.

Method: A sample of 3238 Chinese children (55.02% boys; M_age T1 = 9.89 years) reported semiannually on peer victimization and both externalizing and internalizing problems, and parents reported on their children's externalizing and internalizing problems. Students' objective academic achievement data (i.e. final exam scores) were obtained from school records.

Results: Random intercepts cross-lagged panel modeling (RI-CLPM) revealed that neither academic achievement nor peer victimization mediated the relations between externalizing and internalizing problems in both self and parent reports at the within-person level. The cross-lagged panel models (CLPM) results supported that peer victimization (but not academic achievement) mediated the relations from internalizing to externalizing problems or externalizing to internalizing problems, whether self-reported or parent-reported. This study also identified meaningful sex differences in focal relations among children.

Conclusions: Findings illustrate the importance of distinguishing within-person and between- person associations, with within- person findings failing to support the hypothesized mediating pathways of the Dual Failure or Acting Out Models among children.