A multidimensional developmental neuropsychological model of borderline personality disorder (BPD): examining evidence for impairments in 'executive function'

Borderline Personality Disorder (BPD) is a serious psychiatric disorder characterised by turbulent interpersonal relationships, impaired self image, impulsivity, and a recurrent pattern of unstable affect which is usually evident by early adulthood. It has a community prevalence rate of two per cent, and approximately nine per cent of people diagnosed with BPD commit suicide. This suggests that BPD has one of the highest lethality rates of all psychiatric disorders. The course of the disorder shows a steady improvement over the course of early adulthood with the majority of cases remitting by middle age. This positive but incomplete long-term recovery is thought to be a naturalistic outcome that is independent of treatment effect. The reported study sought to test selected components of a multidimensional developmental neuropsychological model of executive functioning in BPD. The model proposed that BPD is characterised by impairments to four neuropsychological executive functions. These include working memory, response inhibition, affective-attentional bias, and problem-solving. The model further proposed that impaired executive functioning in BPD occurs as a result of the failure of 'experience-dependent' maturation of orbitofrontal structures. These structures are closely associated with the development of the 'cognitive executive'. The study incorporated a cross-sectional design to analyse data from a BPD group, a Depressed Control Group, and a Medical Control Group. The overall findings of the study returned limited support for the original hypotheses. There was no evidence of deficits in working memory, response-inhibition, or problem-solving. In contrast, the BPD group returned some evidence of deficits in affective-attentional bias. Therefore, the results suggest that executive functioning remains largely intact in BPD. This also suggests that people with BPD have the working memory resources necessary to facilitate abstract cognition, have the capacity to effectively plan and execute future-oriented acts, and are able to perform appropriate problem-solving functions. These problem-solving returns are also particularly significant because a number of the tasks utilised in the study are known to be associated with so-called 'frontal-executive' function. These unremarkable findings challenge the view that people with BPD might experience some form of subtle neurological impairment associated with frontal-lobe compromise. The Stroop measure of affective-attentional bias provided the only supportive evidence for the proposed model, and these findings can be accounted for by at least two different explanations. The first suggests that BPD might be characterised by a hypervigilant attentional set. The specific cause of hypervigilance in BPD is unknown, but some candidate factors appear to be the often-reported abuse histories of borderlines, insecure attachment histories, and deficits in parental bonding. The second interpretation suggests that the Stroop findings reflect a form of 'response conflict' in which BPD participants experience difficulties overriding tasks that rely on the enunciation of automatic neural routines. As a result of these findings, further research on the role of arousal, priming, hypervigilance, and response-conflict in BPD is required. It is likely that the Stroop findings reflect a basic, 'hard-wired' attentional mechanism that consolidates by early adolescence at the latest. As a result, the Stroop findings have implications for both the prevention and treatment of BPD. A number of prevention strategies could be developed to address the attentional issues identified in the present study. These include assisting children to more effectively regulate arousal and affect, and assisting parents to communicate affectively with children in order to enhance self-regulation. The treatment implications suggest that interventions directed at affective-attentional processes are required, and further suggest the need for new pharmacotherapies and psychological treatments to modify dysfunctional attentional process. Affective neuroscience will have an increasingly important role to play in the understanding of BPD, and the next quarter century is likely to witness exciting advances in understanding this most problematic of disorders.