Comorbidity in borderline personality: understanding dynamics in development.

Borderline personality disorder is marked by high levels of comorbidity in both adolescent and adult populations. However, the mechanisms involved in the development of comorbidity in BPD remain unclear. To address this issue, the current paper proposes the use of dynamic mutualism theory as a valuable and underexplored framework for investigating comorbidity in BPD from a developmental perspective. Specifically, we discuss how predictions of dynamic mutualism can be extended to better understand the onset, maintenance, and interplay of BPD symptoms with other forms of psychopathology over time. Moreover, we suggest that mutualistic interactions among internalizing and externalizing features throughout early development may foster the emergence of BPD symptoms in adolescence and beyond. Next, we discuss methodological approaches for testing mutualism and review indirect evidence that supports the role of mutualistic processes in the emergence and maintenance of BPD and its comorbidities. We conclude with methodological cautions and recommendations for future studies.