Turner and colleagues (this volume) have written a thoughtful and comprehensive overview of theory and research across a vast literature: environmental and sociocultural influences on the development of personality disorders (PDs). They review behavioral genetics studies and studies on the prevalence of PDs in different countries and from different socioeconomic backgrounds. They describe a wide variety of theories of how PDs develop and review environmental risk factors from early childhood adversity to the quality of communities. This commentary, focusing on borderline PD (for which there is the most research), extends this work in two ways. First, the authors propose an overarching theory of environmental and sociocultural influences on the development of PDs. Second, they add empirical support for two of the theories that Turner and colleagues present: attachment and biosocial theories. In this way, the authors aim to identify processes underlying the development of PDs that may be the focus of interventions. An appropriate intervention at the level of the individual would include Young’s Schema Therapy (Young, 1994), and at the level of the family system the Family Connections Program (Hoffman et al., 2005).