This excerpt was taken from the article Forensic Psychiatry and Forensic Psychology: Personality Disorder

R. Nathan, Mersey Care NHS Trust, Merseyside, UK; University of Liverpool, Liverpool, UK; University of Chester, Chester, UK; and Scott Clinic, Merseyside, UK

H. Wood, Waterloo Manor Hospital, Leeds, UK. The Grange, Cleckheaton, UK

Personality disorder is a clinical concept that is used to describe extremes of personality functioning that has significant negative correlates such as intense distress or gross impairment in performance in work or social domains. It is a broad concept that covers a wide range of enduring psychological dysfunctions that tend to emerge in childhood and persist through the life-course.

Familial/Genetic Factors

Personality disorders are moderately heritable. The etiology of some personality disorders has received more attention than others. The familial aggregation of paranoid, schizotypal, and (to a lesser extent) schizoid personality disorders with schizophrenia supports the positioning of these personality disorders on the schizophrenia-spectrum. There is also some evidence of a specific link between paranoid personality disorder and delusional disorder. There is strong evidence for the role of genetic factors in the development of antisocial and borderline personality disorder. Genes appear to have a more pronounced influence in the early-onset life-course persistent variant of antisocial personality disorder. Current research into the etiology of borderline personality disorder suggests that genetic processes influence the development of underlying processes (such as emotional sensitivity and impulsivity) that confer an increased risk of specific personality disorder traits in the context of particular environmental experiences.

Environmental Factors

Adverse environmental experiences are associated with an increased vulnerability to the development of psychopathology later in life, including personality disorder traits. A range of different adversities (such as physical, sexual, and emotional abuse and neglect) have been demonstrated to increase the risk of personality disorder pathology. It has been proposed that some types of adversity make a specific contribution to the vulnerability for specific types of personality disorder. For example, invalidating responses to the child’s emotions and emotional abuse/neglect have been presented as key adversities associated with borderline personality disorder. Harsh and inconsistent discipline has been linked with antisocial outcomes.

Developmental Pathways

An individual’s personality, whether it is considered disordered or non-disordered, starts to take shape in the context of a two-way interaction between genetic and environmental factors. This is two-way in that on the one hand temperamental characteristics may have an influence on the nature of the environment. For example, infants vary in the degree to which they are liable to express emotions and there is a genetic contribution to this variability. Parents vary in their responses to their child’s expressions of emotions. In some cases, poor parenting may be a response to an infant who displays extremes of emotional expressivity (i.e., over- or under-expression of emotions). On the other hand, parenting or care-giving influences the infant’s developing capacity to reflect on emotions and contain negative emotions. Thus the experience of poor parenting may be associated with the impaired understanding of one’s emotions and a propensity to emotional crises. Interactive influences apply to a range of psychological processes, in addition to emotional expression, such emotional empathy, attributional style, sociability, impulse control, and risk taking. There is a continued interaction over time between the developing profile of psychological functioning and the changing environment. The psychological profile at any one time can be understood as the combination, on the one hand of the effects of interactions between the environmental and psychological processes up to that point and on the other the environmental and psychological demands of the particular developmental stage. These demands are both biologically and socially influenced.

Psychological Processes

Studies of psychological mechanisms have generated clinically useful insights into the etiology of patterns of behavior that are described by personality disorder traits. For example, empathy deficits are thought to account in part for the interpersonal style of patients with narcissistic personality disorder. Exploring the empathy construct reveals that there are varied underlying processes that may be differentially affected in different conditions. Narcissistic personality disorder is thought to be associated with impaired emotional empathy (i.e., the emotional response to the emotional display of others), but with relative preservation of cognitive empathy (e.g., understanding the beliefs of others) (Baskin-Sommers et al., 2014). On the other hand, theory of mind, which is an example of cognitive empathy, is found to be impaired in autism spectrum disorder. The degree of impairment may fluctuate in the same individual at different times. Notably, the picture in borderline personality disorder is of marked impaired emotional empathy (with hyperreactivity to certain cues) when emotionally aroused.

Socio-emotional capacities develop in the interpersonal space between the child and his/her care giver (i.e., the attachment relationship). Attachment theory provides a useful framework to understand both the transactional context in which personality facets develop and how disturbances in early key relationships can influence the development of vulnerabilities to later psychopathology including personality disorder. A number of the psychotherapeutic approaches that have been developed in the treatment of personality disorder, e.g., Mentalization Based Therapy, have their theoretical origin in attachment theory.

Read more about Personality Disorder in the article Forensic Psychiatry and Forensic Psychology: Personality Disorder from the recently published Second Edition of Encyclopedia of Forensic and Legal Medicine. This four-volume set provides a broad overview of forensic and legal medicine, offering reputable, foundational content for researchers and students across the field of forensic and legal medicine that includes cross-referencing to related articles and case studies where further explanation is required. Check out the four-volume set here!