Lowmaster, Sara Elizabeth (2013-08). Mechanisms of Borderline Personality Disorder: The Role of Identity Diffusion. Doctoral Dissertation.
Borderline personality disorder (BPD) is a disabling psychiatric condition that causes pervasive and enduring impairments in social and occupational functioning. Previous literature has outlined the core components of the disorder to include disturbances in affect regulation, identity problems, disrupted interpersonal relationships, and impulsive behavior. While several theories have postulated the primacy of one component in driving the remaining components, the etiological and maintaining mechanisms of BPD are poorly understood. Therefore, the present study examined the primacy of one of these components, identity disturbance, in eliciting changes in the affective, interpersonal, and impulsive components of the disorder. The current study employed an experimental manipulation of identity coherence in 388 undergraduates who were screened for high or low levels of borderline personality features. All participants completed measures of affect prior to and immediately following the manipulation and then completed a GoStop task of impulsivity and an interpersonal trust task in a counterbalanced order. The results suggest individuals with high levels of borderline personality features generally report reduced self-concept clarity and are more susceptible to efforts to alter the coherence of their identity than those with lower levels of borderline personality features. Destabilization of identity coherence led to greater difficulties inhibiting behavior in those with high levels of borderline features, whereas it improved behavioral control in those with low levels of borderline features. These results support theoretical articulations of BPD that indicate impulse control problems are a means of regulating one's internal self-state. Contrary to some characterizations of the disorder, there was no evidence to suggest that alterations of identity coherence led to an exaggerated emotional response or disturbed interpersonal behavior. This finding is consistent with a number of studies examining affective reactivity to emotion induction procedures, interpersonal stimuli, and now alterations in identity coherence indicating that BPD is better characterized by severe, trait negative affect valence compared to healthy controls rather than hyper-reactivity. Moreover, the failure of interpersonal behavior to vary as a function of borderline personality status or experimental task type indicates the importance of dynamic influences during interactions as potential sources for variability in behavior. Although further research is needed to clarify the mechanisms linking identity, affective dysregulation, and interpersonal behavior; psychosocial interventions aimed at maintaining and developing a stable sense of identity may be beneficial for reducing the impulsive behaviors in BPD, which are potentially most critical for establishing the patient's safety.