Biological Basis for Borderline Personality Disorder

Genetic factors appear to be important in the development of borderline personality disorder. For example, core personality traits that characterize this disorder, such as impulsivity and emotional instability, show a high degree of heritability (Livesley, 2008). Also, the rates of borderline personality disorder among relatives of people with this disorder are as high as 24.9% (White, Gunderson, Zanarani, & Hudson, 2003). Individuals with borderline personality disorder report experiencing childhood physical, sexual, and/or emotional abuse at rates far greater than those observed in the general population (Afifi et al., 2010), indicating that environmental factors are also crucial. These findings would suggest that borderline personality disorder may be determined by an interaction between genetic factors and adverse environmental experiences. Consistent with this hypothesis, one study found that the highest rates of borderline personality disorder were among individuals with a borderline temperament (characterized by high novelty seeking and high harm-avoidance) and those who experienced childhood abuse and/or neglect (Joyce et al., 2003).

Risk Factors for Antisocial Personality Disorder

Antisocial personality disorder is observed in about 3.6% of the population; the disorder is much more common among males, with a 3 to 1 ratio of men to women, and it is more likely to occur in men who are younger, widowed, separated, divorced, of lower socioeconomic status, who live in urban areas, and who live in the western United States (Compton, Conway, Stinson, Colliver, & Grant, 2005). Compared to men with antisocial personality disorder, women with the disorder are more likely to have experienced emotional neglect and sexual abuse during childhood, and they are more likely to have had parents who abused substances and who engaged in antisocial behaviors themselves (Alegria et al., 2013).

The table below shows some of the differences in the specific types of antisocial behaviors that men and women with antisocial personality disorder exhibit (Alegria et al., 2013).

Family, twin, and adoption studies suggest that both genetic and environmental factors influence the development of antisocial personality disorder, as well as general antisocial behavior (criminality, violence, aggressiveness) (Baker, Bezdjian, & Raine, 2006). Personality and temperament dimensions related to this disorder, including fearlessness, impulsive antisociality, and callousness, have a substantial genetic influence (Livesley & Jang, 2008). Adoption studies clearly demonstrate that the development of antisocial behavior is determined by the interaction of genetic factors and adverse environmental circumstances (Rhee & Waldman, 2002). For example, one investigation found that adoptees of biological parents with antisocial personality disorder were more likely to exhibit adolescent and adult antisocial behaviors if they were raised in adverse adoptive family environments (e.g., adoptive parents had marital problems, were divorced, used drugs, and had legal problems) than if they were raised in a more normal adoptive environment (Cadoret, Yates, Ed, Woodworth, & Stewart, 1995).

Researchers who are interested in the importance of the environment in the development of antisocial personality disorder have directed their attention to such factors as the community, the structure and functioning of the family, and peer groups. Each of these factors influences the likelihood of antisocial behavior. One longitudinal investigation of more than 800 Seattle-area youth measured risk factors for violence at 10, 14, 16, and 18 years of age (Herrenkohl et al., 2000). The risk factors examined included those involving the family, peers, and community. A portion of the findings from this study are provided in Figure 2.

Those with antisocial tendencies do not seem to experience emotions the way most other people do. These individuals fail to show fear in response to environmental cues that signal punishment, pain, or noxious stimulation. For instance, they show less skin conductance (sweatiness on hands) in anticipation of electric shock than do people without antisocial tendencies (Hare, 1965). Skin conductance is controlled by the sympathetic nervous system and is used to assess autonomic nervous system functioning. People become aroused and anxious when the sympathetic nervous system is active and sweat gland activity increases. Thus, increased sweat gland activity, assessed through skin conductance, indicates arousal or anxiety. For those with antisocial personality disorder, a lack of skin conductance may indicate the presence of characteristics such as emotional deficits and impulsivity that underlie the propensity for antisocial behavior and negative social relationships (Fung et al., 2005).

While emotional deficits may contribute to antisocial personality disorder, so too might an inability to relate to others’ pain. In a recent study, 80 prisoners were shown photos of people being intentionally hurt by others (e.g., someone crushing a person’s hand in an automobile door) while undergoing brain imaging (Decety, Skelly, & Kiehl, 2013). Prisoners who scored high on a test of antisocial tendencies showed significantly less activation in brain regions involved in the experience of empathy and feeling concerned for others than did prisoners with low scores on the antisocial test. Notably, the prisoners who scored high on the antisocial test showed greater activation in a brain area involved in self-awareness, cognitive function, and interpersonal experience. The investigators suggested that the heightened activation in this region when watching social interactions involving one person harming another may reflect a propensity or desire for this kind of behavior.

Narcissistic Personality Disorder

Narcissistic personality disorder (NPD) is characterized by the personality traits of persistent grandiosity, an excessive need for admiration, and a personal disdain and lack of empathy for other people. As such, an individual with narcissistic personality disorder (NPD) usually displays arrogance and a distorted sense of personal superiority and seeks to establish abusive power and control over others. Self-confidence (a strong sense of self) is a personality trait different from the traits of narcissistic personality disorder; thus, people with narcissistic personality disorder (NPD) typically value themselves over others to the extent of openly disregarding the wishes and feelings of anyone else and expect to be treated as superior, regardless of their actual status or achievements. Socially, the person with NPD usually exhibits a fragile ego (self-concept), intolerance of criticism, and a tendency to belittle other people to validate their own superiority.  People with NPD often spend much time daydreaming about achieving power and success or on their appearance.

Risk Factors for Narcissistic Personality Disorder

The lifetime rates of narcissistic personality disorder are estimated at 1% in the general population and between two to 16% in the clinical population. People with the diagnosis in recent years have spoken out about its stigma in media and possible links to abusive situations and childhood trauma. Such narcissistic behavior typically begins by early adulthood and occurs across a broad range of situations. The causes of narcissistic personality disorder are unknown but theorized to be linked to certain types of traumas. A combination of genetic, environmental, and social factors are involved in narcissistic personality disorder.

Narcissistic personality disorder usually develops either in adolescence or in early adulthood, and it is common for children and adolescents to display personality traits that resemble NPD, but such occurrences are usually transient and register below the clinical criteria for a formal diagnosis of NPD. True symptoms of NPD are pervasive, apparent in varied social situations, and are rigidly consistent over time. Severe symptoms of NPD can significantly impair the person’s mental capabilities to develop meaningful human relationships, such as friendship, kinship, and marriage. Generally, the symptoms of NPD also impair the person’s psychological abilities to function socially, either at work, at school, or within important societal settings. The DSM-5 indicates that to qualify as symptomatic of NPD, the person’s manifested personality traits must substantially differ from the cultural norms of society.

The reason for such an indirect path to psychotherapy is partly because individuals with NPD generally possess poor insight and are unaware that their actions produced their mentally unhealthy circumstance, and so fail to recognize that their perceptions and behaviors are socially inappropriate and problematic, because of their very positive self-image (inflated self-concept).

The occurrence of narcissistic personality disorder presents a high rate of comorbidity with other mental disorders. People with NPD are prone to bouts of psychological depression, often to the degree that meets the clinical criteria for a co-occurring depressive disorder. Moreover, the occurrence of NPD is further associated with the occurrence of bipolar disorder and substance use disorders, especially cocaine use disorder.