Treatment
Developmental factors
Childhood trauma
There is a strong correlation between child abuse, especially child sexual abuse, and development of BPD. Many individuals with BPD report a history of abuse and neglect as young children, but causation is still debated. Patients with BPD have been found to be significantly more likely to report having been verbally, emotionally, physically, or sexually abused by caregivers of either gender. They also report a high incidence of incest and loss of caregivers in early childhood. Individuals with BPD were also likely to report having caregivers of both sexes deny the validity of their thoughts and feelings. Caregivers were also reported to have failed to provide needed protection and to have neglected their child's physical care. Parents of both sexes were typically reported to have withdrawn from the child emotionally and to have treated the child inconsistently. Additionally, women with BPD who reported a previous history of neglect by a female caregiver and abuse by a male caregiver were significantly more likely to experience sexual abuse by a non-caregiver.
Neurological patterns
The intensity and reactivity of a person's negative affectivity, or tendency to feel negative emotions, predicts BPD symptoms more strongly than does childhood sexual abuse. This finding, differences in brain structure, and the fact that some patients with BPD do not report a traumatic history, suggest that BPD is distinct from the post-traumatic stress disorder which frequently accompanies it. Thus, researchers examine developmental causes in addition to childhood trauma.
Research published in January 2013 by Dr. Anthony Ruocco at the University of Toronto has highlighted two patterns of brain activity that may underlie the dysregulation of emotion indicated in this disorder: (1) increased activity in the brain circuits responsible for the experience of heightened emotional pain, coupled with (2) reduced activation of the brain circuits that normally regulate or suppress these generated painful emotions. These two neural networks are seen to be dysfunctionally operative in the frontolimbic regions, but the specific regions vary widely in individuals, which calls for the analysis of more neuroimaging studies.
Mediating and moderating factors
Executive function
While high rejection sensitivity is associated with stronger symptoms of borderline personality disorder, executive function appears to mediate the relationship between rejection sensitivity and BPD symptoms. That is, a group of cognitive processes that include planning, working memory, attention, and problem-solving might be the mechanism through which rejection sensitivity impacts BPD symptoms. A 2008 study found that the relationship between a person's rejection sensitivity and BPD symptoms was stronger when executive function was lower and that the relationship was weaker when executive function was higher. This suggests that high executive function might help protect people with high rejection sensitivity against symptoms of BPD. A 2012 study found that problems in working memory might contribute to greater impulsivity in people with BPD.
Family environment
Family environment mediates the effect of child sexual abuse on the development of BPD. An unstable family environment predicts the development of the disorder, while a stable family environment predicts a lower risk. One possible explanation is that a stable environment buffers against its development.
Self-complexity
Self-complexity, or considering one's self to have many different characteristics, appears to moderate the relationship between Actual-Ideal self-discrepancy issues and the development of BPD symptoms. That is, for individuals who believe that their actual characteristics do not match the characteristics that they hope to acquire, high self-complexity reduces the impact of their conflicted self-image on BPD symptoms. However, self-complexity does not moderate the relationship between Actual-Ought self-discrepancy and the development of BPD symptoms. That is, for individuals who believe that their actual characteristics do not match the characteristics that they should already have, high self-complexity does not reduce the impact of their conflicted self-image on BPD symptoms. The protective role of self-complexity in Actual-Ideal self-discrepancy, but not in Actual-Ought self-discrepancy, suggests that the impact of conflicted or unstable self-image in BPD depends on whether the individual views himself or herself in terms of characteristics that they hope to acquire, or in terms of characteristics that they should already have acquired.
Thought suppression
A 2005 study found that thought suppression, or conscious attempts to avoid thinking certain thoughts, mediates the relationship between emotional vulnerability and BPD symptoms. A later study found that the relationship between emotional vulnerability and BPD symptoms is not necessarily mediated by thought suppression. However, this study did find that thought suppression mediates the relationship between an invalidating environment and BPD symptoms.