Borderline personality disorder, mentalization, and the neurobiology of attachment.

We discuss the neural and neurobiological underpinnings of the core features of borderline personality disorder (BPD), including emotion dysregulation, impulsivity, disturbed interpersonal functioning, identity diffusion, and feelings of inner pain. We review neurobiological research that supports a developmental, biobehavioral switch-model of the relationship between mentalization, stress, and attachment. Although it is likely that there are different developmental pathways to BPD, involving complex interactions between environmental, biological, and psychosocial factors, the final common outcome of these pathways is a low threshold for the activation of the attachment system and for deactivation of controlled mentalization, coupled with impairments in the ability to differentiate mental states of self and other. This leads to hypersensitivity and increased susceptibility to contagion from other people's mental states, poor integration of cognitive and affective aspects of mentalization, and dysfunctions in stress-regulation systems. The treatment implications of this neurobiologically informed model of BPD are discussed.