Project 454859

Children and adolescents are particularly sensitive to developing externalizing (EXT; attention-deficit/hyperactivity, oppositional, conduct symptoms) and internalizing (INT; anxiety, depressive, phobia symptoms) psychopathology. The development of psychopathology during childhood and adolescence also increases risk for chronic psychopathology throughout the lifespan. EXT and INT commonly co-occur, and co-occurrence is associated with greater symptom severity and poorer treatment response. However, it is currently unknown which specific symptoms co-occur and how these associations are shaped across early development. This is because past research has: a) focused on summary scales rather than symptoms; b) used analytic approaches that do not test how individuals' symptoms compare to others' symptoms (between-person effects) and individuals' own deviations in symptoms (within-person effects); and c) failed to account for daily dynamic variations in symptoms. To address these shortcomings, this project aims to create new knowledge on the co-development of EXT and INT symptoms through childhood and into early adolescence. Through two studies, the present project will: 1) test associations between EXT and INT symptoms through childhood and into early adolescence with a large, longitudinal dataset (N=1339); and b) conduct a study examining the daily dynamic EXT and INT symptom associations in a sample of Canadian early adolescents (N=400) using ecological momentary assessment-a method that uses digital technology to gather real-time responses. Both studies will use an analytic approach that elucidates between- and within-person effects. Early recognition of EXT and INT symptoms will enable more effective targeting of treatment. Findings from this project will produce new knowledge on the co-development of early EXT and INT symptoms that can be used to optimize strategies by practitioners to enhance the mental health of children and adolescents.