Externalizing psychopathology is highly prevalent in children and adolescents. Yet, current understanding of the externalizing psychopathology spectrum is predominantly founded on cross-sectional and conventional longitudinal designs. Compared to these designs, intensive longitudinal data have greater ecological validity and provide insight into within-person fluctuations and short-term developmental dynamics. In this Special Issue, we bring together a selection of 10 innovative and original empirical articles to demonstrate the benefits of intensive longitudinal data for understanding the development of the externalizing psychopathology spectrum during childhood and adolescence, as well as one thoughtful commentary from leaders in the externalizing psychopathology field. In this Introduction to the Special Issue, we describe the articles included in this Special Issue in relation to study designs, timescales, samples, and statistical modeling techniques. We conclude by considering the implications of intensive longitudinal data for informing and enhancing our understanding of externalizing psychopathology with child and adolescent samples, as well as critical future research directions.
