Beyond comorbidity: Toward a dimensional and hierarchical approach to understanding psychopathology across the life span.

We propose a novel developmentally informed framework to push research beyond a focus on comorbidity between discrete diagnostic categories and to move toward research based on the well-validated dimensional and hierarchical structure of psychopathology. For example, a large body of research speaks to the validity and utility of the internalizing and externalizing spectra as organizing constructs for research on common forms of psychopathology. The internalizing and externalizing spectra act as powerful explanatory variables that channel the psychopathological effects of genetic and environmental risk factors, predict adaptive functioning, and account for the likelihood of disorder-level manifestations of psychopathology. As such, our proposed theoretical framework uses the internalizing and externalizing spectra as central constructs to guide future psychopathology research across the life span. The framework is particularly flexible, because any of the facets or factors from the dimensional and hierarchical structure of psychopathology can form the focus of research. We describe the utility and strengths of this framework for developmental psychopathology in particular and explore avenues for future research.