1. Introduction

Borderline Personality Disorder (BPD) is related with a biological sensitivity to over-anxiety and over-reactivity that is related to adverse situations, according to biosocial theory. However, psychophysiological findings in BPD suggest that BPD is related to hypo-anxiety as well as hypo-responsiveness to non-emotional stimuli. Due to the complexity of emotion dysregulation in BPD, emotion coherence theory has been proposed as an alternative way of conceptualizing the role of psychophysiology in BPD. A central feature of BPD is emotion dysregulation. BPD has been recognized as a long-term mental illness in which patients are predisposed to develop emotional dysregulation biologically with baseline overstimulation, overreaction, and impaired habituation. Nevertheless, according to a self-report perspective, psychophysiological indicators show evidence of lower but not higher levels of anxiety, as well as huge differences in reactivity between individuals with BPD and controls. There is evidence suggests that habituation to psychophysiological markers is impaired in patients with BPD. In conclusion, mixed results were presented for the claim regarding excessive anxiety and over-reactivity in patients with BPD. Multiple symptom trajectories can be used to diagnose BPD. Psychophysiological arousal and reaction are impacted by dissociation and trauma, as well as the emotional significance of the stimuli [1].

The central feature belong to borderline personality disorder (BPD) can be emotional derangement. It is associated with an abnormal and an extremely intense fear about being abandoned by others. Patients with BPD not only have a fear of real abandonment, but also react to the threat of imagined abandonment. They tend to idealize their partner and ask for more time and share intimate details early in the relationship. However, they soon would switch back and forth between extreme idealization and extreme devaluation of others. They often vent their anger by putting others down and are often suspicious of their partner. In this setting, the individuals are repeatedly dismissed by significant others, often through the expression of neglectful or punitive emotions. At the same time, they demonstrate emotional impulsivity. They have intense and uncontrollable anger towards others and a strong tendency toward suicidal and self-harming behavior. In that case, BPD has a negative impact on the patients themselves and probably harms surrounding people. Thus, it is important to understand the development of BPD. In fact, the factors in BPD development are various and complex. There are many types of research to explore the influential factors in BPD development. There is a relationship between various types of childhood maltreatment and the perception of parenting style by BPD patients. Maltreatment in childhood can be divided into emotional maltreatment and physical maltreatment [2]. However, because abuse frequently happens in the context of dysfunctional families, it can be difficult to differentiate the impacts of the family environment from the consequences of maltreatment. Patients with BPD symptoms are also more likely to have suffered childhood adversity, according to previous studies [2].

There are various scientific based treatments for BPD. Dialectical behavior therapy (DBT) is a treatment that mitigated the most difficult aspects of traditional therapy. There have been 13 manual bar therapy tests for BPD, and five major methods: schema-focused therapy (SFT), systems training for emotional predictability and problem solving (STEPPS), dialectical behavioral therapy, transference-focused psychotherapy (TFP), and mentalization-based treatment (MBT) [3]. DBT is the best-known and most widely used treatment incorporated debate and validation into therapy that focuses on skill building and behavior shaping. In MBT, mentalization refers to the ability to understand the perspective or belief of another person. It stabilizes BPD by strengthening the patient’s ability to understand the views of others under stressful circumstances. TFP is a manual psychoanalytic-oriented psychotherapy that enables the patient to achieve a balanced and coherent way of thinking about himself and others. SFT is a comprehensive cognitive therapy used to change the patient's personality structure by changing negative thoughts and feelings, so that the emotional state would be under the control of the patient. There are three parts to STEPPS. The first is psychological education, redefinition, and correcting misconceptions. The second is improving management skills, and the third is behavioral management skills and avoiding self and interpersonal injuries [3].

According to biosocial theory, BPD is caused by a mix of physiological over-anxiety and over-reaction, as well as a vulnerability to ineffective surroundings, while psychophysiological research has demonstrated the contrary. The degree of anxiety and relevant psychophysiological markers was relatively low from the perspective of the patients, whereas there were some disparities between the response of BPD patients and the control group. Psychophysiology and reaction are influenced not only by the emotional level of the input but also by how elements like trauma or isolation are perceived. BPD is defined by emotional disturbance, which includes an excessively great fear of being abandoned by others. It is important to understand the negative effects of maltreatment during childhood on BPD development. This review aims to explore this area by first analyzing different types of childhood maltreatment and their impacts on the risk of BPD. Protective factors, such as resilience and relevant personality traits, were also discussed by analyzing sibling studies. At the end, relevant vulnerable factors in BPD were discussed. This review can provide guidance for the development of prevention programs for at-risk families in communities and schools.

2. Factors in BPD Associated Childhood Maltreatment

2.1. The Impact of Different Types of Childhood Maltreatment

The maltreatments that kids might encounter can be divided into four types: emotional, sexual, physical abuse, and emotional and physical neglect. Emotional abuse is a type of abuse that involves a person or persons causing a serious threat to the mental health of the abused person through seemingly harmless words, accusations, inferences, and non-verbal innuendoes towards a specific subject. Emotional abuse, meanwhile, is a form of hidden psychological violence and a manifestation of an excessive desire to control the other half, but it is harder to detect than direct psychological violence. Sexual abuse is defined as actual or threatened physical aggression for the purpose of satisfying sexual desire. Sexual abuse also includes having sexual relations with a child in any situation. A non-accidental physical injury caused by a caregiver to a child that results in death, physical disfigurement, impairment, loss of bodily function, or putting the child in a situation where such injury is likely to occur. Emotional and physical neglect is likely to result in a person being emotionally numb, anti-dependent, and unable to care for themselves or others. Hernandez et al. draw a sample of females with a wide age interval, and these patients completed the self-report instruments to examine the relationship between different types of maltreatment and the effect of BPD. Also, they measured and compared the data of different types of maltreatment in BPD, other PD, and Non-PD groups. It can be found that all kinds of maltreatment are related to BPD. The result of the previous study supports the relationship between sexual and emotional abuse in childhood and BPD, but there is not have enough evidence to show the association between style of parenting and BPD. Moreover, sexual abuse can cause a shattered sense of boundaries for people, who may not think they are part of the world. The people who encountered the emotional abuse probably had experienced abandoning or betraying by others, so they cannot believe others anymore. Regarding other types of maltreatment, previous research did not find a significant relationship between them and BPD. The main factors of BPD are related to sexual abuse and emotional abuse. Sexual abuse might have a negative influence on the sense of boundary, which is related to the BPD symptoms [2]. It indicates that there is a significant relationship between childhood maltreatment and borderline personality disorder. Plus, it can be speculated that the past experiences of emotional abuse might cause the current overstimulation, fear of abandonment, and erratic behavior in BPD.

Negative parenting may influence the development of BPD. Additionally, this relationship can be a reciprocal one. Stepp and his cooperators studied a sample of four cohorts of female with different intervals of age. The result shows that symptoms of BPD remained stable from the age of fourteen to seventeen. Subsequently, the researchers surveyed the parents of BPD patients across different ages, in order to study the impacts of punishment and the low parental warmth. Low parental warmth was measured by caregiver reports. These analyses provide a comprehensive examination of the nature of reciprocity between parenting practices, particularly harsh punishment and low warmth from caregivers, and the child. There is a significant correlation between BPD symptoms and adolescent parenting styles [4]. It can demonstrate that specific negative parenting practices and BPD symptoms exert bidirectional influences in adolescent girls. BPD symptoms in adolescents may increase the caregiver's harsh punishment and low warmth treatment, and the caregiver's punishment and low warmth may also increase BPD symptoms.

2.2. The Effects of Resilience

Traits are neurobiological features possessed by an individual that has the power to influence an individual's behavior. It allows the individual to give consistent reactions in a changing environment. The study investigated the association of adverse childhood experiences and personality traits with BPD by comparing women with BPD and their sisters. Participants are female BPD patients and their sisters. All sisters had to be full siblings who had lived with at least one of their natural parents while growing up. The results of the study indicated that there was no strong relationship between childhood adversity and BPD symptoms. However, both groups reported a high prevalence of dysfunctional parent-child relationships and childhood trauma. Their childhood adversity and the abuse they experienced were similar, so the main reason for the difference between the sisters was a difference in resilience. The view that personality traits play an influential role in resilience can be supported by the research findings [5]. This implies that even if two individuals share the same childhood encounter, they may not both develop psychological disorders, or the same psychological disorder, due to their own different personality traits.

Resilient children can cope better with problems. It is found within the text that some children who are abused have psychological problems and may develop a borderline personality disorder, but children who are not abused also develop BPD as adults. Women have adaptive mechanisms that make them vulnerable to BPD, and those who are vulnerable to BPD have a high rate of childhood trauma. With child maltreatment outcomes also connected with disparities across families, 56 pairs of sisters were evaluated in a resilience study. Each pair of sisters had endured serious childhood abuse, according to the study, and just one pair of sisters had no exceedingly rare disorders. Different results were made from a pair of sisters who had experienced catastrophic childhood abuse and home environment disturbance. Sisters without BPD were more upbeat and didn't have this vulnerability. Due to personal, family, and environmental circumstances, sisters were more prone to develop BPD [6].

3. Childhood Maltreatment and the Vulnerable Factors in BPD

Neuroticism is a kind of personality trait with a certain neurotic tone. People with neuroticism have an experiential preference for negative events. Neuroticism often has a negative impact on an individual's career, love, life, and relationships. It can even lead to the development of neurosis or other physical and mental disorders. Using stratified random sampling, the researchers selected 282 eligible patients and made clinical diagnoses. Of the patients with BD, 36.3% were type I (BD-I), 55.5%were type II (BD-II), and 8% were type unspecified (BD-NOS). Patients with BD-II and BD-NOS were assigned to the same group. Through research, it can be found that many BPD patients have comorbidities with other mental diseases, e.g., bipolar disorder and unipolar disorder. Researchers investigated psychopaths with unipolar or bipolar disorder and their associations with self-reported borderline personality disorder traits and found that self-reported BPD traits were strongly associated with self-reported neuroticism. Plus, self-reported childhood trauma is moderately related [7]. There was a modest correlation between self-reported childhood traumatic experiences and attachment in adulthood. It can be speculated that the manifestations of neuroticism in other psychiatric disorders coexisting with BPD are likely to interact with the symptoms of BPD.

Cognitive and emotional inclinations can alter expectations and perceptions under social exclusion. Emotional differences are associated with brain differences. People who are sensitive to rejection will take it very seriously and will think a lot of negative information. A study on the severity of sensitivity to rejection (RS) in BPD patients at different stages was conducted. 167 women (77 acute BPD, 15 BPD in remission, 75 matched healthy controls) were selected. RS is defined as anxiety towards the expectation of rejection. Experimental results showed that the sensitivity to rejection scores of acute and remission BPD patients were higher than those of healthy controls. Childhood maltreatment may be related to symptom severity, RS, and self-esteem. There is a significant relationship between RS and self-esteem. Plus, increased symptoms of BPD are negatively related to attraction and acceptance. BPD patients' sensitivity to rejection contributes to social dysfunction and bias. Individuals with high RS overrate rejection and feel that they have been hurt and rejected by their peers frequently [8].

This study mainly examined the differences between BPD patients and depressive disorders (DD) patients in child abuse and emotional management difficulties. 305 participants, 177 BPD patients and 128 DD patients completed the questionnaire, and it was found that BPD patients showed more child abuse and emotion regulation difficulties than DD patients. It was found that BPD patients are more likely to have child abuse in childhood than DD patients. This result showed that the core features of BPD is having serious difficulties in emotional regulation. In all the subscales of the Emotion Regulation Scale (DERS), the score of patients with BPD is higher than DD. Patients with BPD have significant difficulties in emotion regulation and impulse control [9]. Mindfulness refers to the ability to be aware of the presence. BPD patients have the defect of mindfulness during the treatment process. Impulsivity and sexual abuse were found to be significant predictors of mindfulness capacity in BPD. Temperament traits have no moderating effect on childhood sexual abuse and mindfulness. Neuroticism and impulsivity of BPD are significantly negatively correlated. Sexual abuse is severe and have a long-term impact in mindfulness capacity of BPD [10].

4. Conclusions

To sum up, the factors that impact the development of BPD are complicated. There is no direct causal relationship between the factors and the BPD, based on previous studies. Only significant correlations between them were found. The abuse that was experienced by a person in childhood, particularly sexual and emotional abuses, is likely to undermine that person's sense of boundaries and increase the risk of developing BPD. The family environment, in which a person grows up, with harsh punishments and low warmth from caregivers, is likely to have a bidirectional effect on the development of BPD. Differences in personality profiling between people who have experienced similar hardships might serve as a protective factor. Resilience is also a crucial aspect to prevent the abused child from developing BPD.

One limitation of previous studies is that the interviews of childhood maltreatment were done after the patient grew up and was diagnosed with BPD. Future studies should target at-risk children and conduct longitudinal studies from childhood. Another limitation of previous research is that vulnerable factors in BPD were instigated individually. Future studies can investigate the interaction between different vulnerable factors in BPD. This review emphasized the importance to develop early prevention and intervention programs in schools and communities, through analysing the childhood maltreatment literature in BPD. Future psychoeducational programs that serve at-risk children and families should incorporate both protective and vulnerable factors into the curriculum.