In sum, we describe an alternative pathway to the more typically studied externalizing model for SUDs that we refer to as the internalizing pathway. In this model, we identify the markers that identify progression along the internalizing pathway ranging from the emergence of behavioral inhibition in infancy and toddlerhood to the development of Negative Affect SUDs in young adulthood. By identifying markers of progression along this pathway, we articulate a model marked by heterotypic continuity in problem manifestation.
