In this commentary, the authors note that Gratz and colleagues (2014) have made an important step in understanding the effect of maternal borderline personality (BP) pathology on children's developing emotion regulation. The emphasis on mechanisms of transmission in their article has implications for our understanding of the relationships between parental mental health and child functioning more generally. The authors of the commentary argue that using a biopsychosocial framework to understand the multiple levels that characterize the developmental system will push this kind of focus on behavioral mechanisms a step further. A biopsychosocial framework implies that a set of hierarchically organized, but reciprocally interacting, processes, from the genetic to the environmental, provide the essential elements of development (Gottlieb, 2007). Thus, in studying the effects of maternal BP pathology on child outcomes, consideration may also be given to the role of underlying biological processes that are influenced by maternal functioning and may alter child outcomes. Challenges to using this general approach in studying the effects of parental psychopathology are discussed.