Introduction

An ongoing debate has been whether mental disorders derive from biological factors or environmental factors. Although there are studies out there that give insight on the question, it is hard to know what the real answer is. I would like to do research on the question regarding whether mental disorders derive from nature or nurture. Although it is unlikely I will find the answer with my research, I would still like to highlight the research that has been done on the topic therefore I can formulate my own opinions. In this paper, I will review some of the medical research that has been done on mental disorders. I will discuss the characterization of borderline personality disorder, the suspected causes, neurobiological factors, genetic susceptibility, epigenetics, DNA methylation, and environmental causes.

Literature Review

In order to understand the root causes of borderline personality disorder, it is first important to understand what it is. Kulacaoglu and Kose (2018) define borderline personality disorder (BPD) as a chronic psychiatric disorder that includes patterns of instability, distorted self-image, unstable personal relationships, impulsivity, and suicidal ideation. It is also characterized as an emotionally unstable personality disorder. Individuals with this disorder are vulnerable to social and interpersonal stressors, and emotional hyperarousal. These two factors are caused by neurological abnormalities that take place in the brain. These abnormalities may cause difficulties with attachment, social cognition, and social reward. Individuals with borderline personality disorder may have a harder time regulating their emotions and keeping interpersonal relationships intact.

There is no known cause of borderline personality disorder, yet there have been multiple studies to try and understand it. It is proposed that it is caused by psychosocial, genetic, and neurobiological factors that interfere with brain development (Kulacaoglu & Kose, 2018). In terms of neurobiological factors, there has been neurological research data that proposes neuropeptide functions can be the root cause in BPD patients. Hypothalamic pituitary adrenal axis dysfunction and decreased oxytocin levels are also factors that have been said to cause BPD. Numerous studies report bilateral reductions in the hippocampus, amygdala, and medial temporal lobe in BPD patients. A reduction in these areas may be the cause of the impulsivity that a patient may feel or experience. It would also explain the emotional dysregulation of patients with borderline personality disorder. These factors show us that neurobiological factors presumably play a big role in the development of BPD.

In terms of psychosocial and environmental factors, trauma and neglect are the two main factors that are presumably the cause of this disorder. Multiple studies report that childhood abuse, emotional neglect, and inconsistent caretaking can cause borderline personality disorder to develop in an individual. In a study with 500 individuals, it was reported that children who were physically abused or neglected as a child met the criteria to be considered an individual with borderline personality disorder in adulthood (Kulacaoglu & Kose, 2018). Another study reported that childhood abuse and neglect were a significant cause of BPD in adulthood. Mainali, Rai, and Rutkofsky (2020) review the risk factors for developing borderline personality disorder. Their research states that among all personality disorders, 30% to 90% of patients who meet the criteria for BPD have a history of childhood abuse or trauma. These findings suggest that environmental factors may play a large role in the development of borderline personality disorder.

Kulacaoglu and Kose (2018) discuss the possibilities of the origin of borderline personality disorder and also talk about how it is displayed in an individual. They propose that a factor in developing this disorder may be one’s life experiences. Childhood trauma is prevalent in those with BPD, however, not everyone diagnosed with borderline personality disorder may have childhood trauma. In a study of 500 individuals, researchers found that children who were sexually abused, physically abused, verbally abused, or neglected were more likely to meet the criteria of having borderline personality disorder in adulthood. Another study conducted reported that childhood abuse and trauma had a significant effect on a diagnosis of borderline personality disorder in adulthood. Since individuals with borderline personality disorder may not have a history of childhood abuse or trauma, it is hard to indicate that there is a positive correlation between the two. However, there is sufficient evidence that suggests that life experiences do have at least some impact on the development of an individual.

Kulacaoglu and Kose (2018) also discuss the correlation between trauma history and borderline personality disorder. Having a history of trauma may trigger or activate genetic predisposition. Traumatic experiences make an individual more prone to having altered behavioral tendencies. These behavioral tendencies may look like the DSM-5 factors that diagnose an individual with borderline personality disorder. Such factors would be frequent mood swings, suicidal behavior, self-injury, unstable self-image, unstable relationships, fear of abandonment, frequent loss of temper, and unsafe behaviors (Millard, 2022). Borderline personality disorder is also reported to coincide with another mental illness. Such illnesses may be obsessive-compulsive disorder, depression, antisocial personality disorder, and narcissistic personality disorder. Anybody with a diagnosis of any of these disorders listed may also have a high probability of one of these illnesses coinciding with it.

There are a couple of factors that may determine whether one develops borderline personality disorder or not. The first factor would be, as previously stated, environmental factors and social factors. The prevalence of having BPD in those who have a history of traumatic life experiences or abandonment is high. Family history is also another factor that may contribute to this illness. Having a first-degree relative with borderline personality disorder (parent or sibling) is at a higher risk for developing BPD. Studies suggest that borderline personality disorder has an estimated heritability of about 40%. The last factor that may contribute to developing this disorder has to do with brain structure. Findings suggest that those diagnosed with BPD may have structural differences in their brain, which alter impulse control and emotion regulation.

Moley, Norman, & Coccaro (2022) examine the correlation between mild traumatic brain injuries (mTBI) and neurological disorders. Symptoms of mTBI include mood symptoms, sleep disturbances, and emotional lability. Having this diagnosis increases one's risk of suicide, mood disorders, and psychotic disorders. There has been a positive correlation between the evidence of violence and aggression and personality disorders, such as borderline personality disorder. Their findings show that individuals with antisocial personality disorder or borderline personality disorder are more likely to exhibit disregard for rules and anger dysregulation. Those with a history of mild traumatic brain injuries also show a reduction in white matter functioning throughout the brain. Veterans who have had a brain injury show white matter abnormalities. Their study also finds that a reduction in gray matter has been shown in subjects with borderline personality disorder compared with healthy controls. These findings suggest that there is a probable positive correlation between brain injury and the development of borderline personality disorder.

The articles reviewed give a thorough understanding of how borderline personality disorder may be developed in an individual. They discuss genetic factors, neurobiological factors, and environmental factors. Although these articles give great insight on BPD, there is still a lot of information that is unknown. Most studies focus on the biological and genetic factors that contribute to the disorder, but I would like to focus more on the environmental factors. Multiple studies exclude the direct effects of childhood instances on the development of borderline personality disorder. For my study, I plan to ask direct questions to people who have a diagnosis of borderline personality disorder. I would like to review what instances they encountered during their childhood that may have caused the disorder to develop over time.

Methods

This study will be conducted through a survey with multiple different questions and reviewing different outlooks on the environmental factors of BPD. In my study, I plan to conduct a survey of participants with borderline personality disorder. My participants were gathered through a mental health forum focused on borderline personality disorder that I found online. In this forum, I posted my survey and encouraged others to fill out the survey if they felt comfortable. This way I was targeting individuals with borderline personality disorder but was not specifically telling them it had to do with borderline personality disorder so that my results wouldn’t be biased or varied. For my control group, I sent the survey to other individuals I know and had them complete the survey for me. I knew that these individuals did not have borderline personality disorder, so that is why I chose them for my control group.

Due to the fact that BPD is presumably developed because of childhood traumas, I would like to highlight the individual's childhood throughout the survey. In this survey, I plan to include questions that the participant can answer yes, no, sometimes, or unsure of. I have also included the option “I do not wish to answer” in case they feel uncomfortable answering the question at hand. Participants will be asked questions regarding their childhood, genetics, and any possible or previous brain injuries. The questions will include instances of parental neglect, bad influences in the household, physical or emotional abuse, parental separation or loss, inheritable genetics, and brain injuries. I also will have a control group that does not have borderline personality disorder to show the difference between childhood backgrounds.

After gathering all of my data, I plan to use a chi-square test to determine if there is a positive correlation between my variables or not. I will also display a bar graph to show the differences between those with borderline personality disorder and those without it. I will compare the questions and answers that I have received and see if there are any specific differences. These answers will show me data regarding whether borderline personality disorder is developed from childhood traumas, genetics, or brain injuries.

The participants are made aware that the survey will be used for the study at the beginning of the survey. They will then have the option to continue the survey or exit out of it. At the end of the survey there is also an option to submit the survey or not. Participants are made aware that answers are anonymous, and their identities will not be exposed throughout the experiment results.

Results

Results, graphs, chi-square tests, and interview questions have been removed for confidentiality purposes and out of respect for the participants. If you would like to learn more about this study, please feel free to reach out to me through my contact page.

Discussion

In this study, I aimed to explore the root causes of borderline personality disorder (BPD) and understand why it develops in an individual. My goal was to examine the correlation between BPD and factors such as home environment, childhood abuse or neglect, traumatic brain injuries, and genetic influences. My hypothesis posited that environmental factors are the primary cause of BPD, and that all the listed factors contribute to its development.

My results largely supported my hypothesis, as the data demonstrated significant correlations with the factors I investigated. While traumatic brain injuries did not show a strong positive correlation with BPD in this study, I found a notable positive correlation between childhood trauma and genetic inheritance in the development of BPD. This aligns with some of the earlier research highlighted in the literature review, which suggested that genetics and environmental factors might play a role in the development of BPD.

Although my findings did align with the general expectations of the hypothesis regarding environmental and genetic factors, they differed from some of the previous studies reviewed, which showed more widespread correlations between environmental, genetic, and brain trauma factors. The main difference may stem from the larger sample sizes used in those studies, which could have provided more robust data. I believe that a higher number of participants in my own study would have potentially strengthened the evidence for the environmental and genetic correlations with BPD.

Despite these differences, I maintain that these factors—environmental and genetic—are likely contributors to the development of BPD. However, brain trauma did not show the same correlation in my study. If the study were to be conducted again with a larger sample size, I expect the results might provide more comprehensive insights into the connections between these factors and the disorder. To improve future research, I would aim to gather a broader, more diverse participant pool to enhance the reliability of the data and findings.