Chapter 2 – How does personality disorder develop

The biopsychosocial model

Despite professional disagreements, it would be reasonable to state that currently, most experts in the field subscribe to the biopsychosocial model for understanding the development of personality disorder.

What does this mean? Personality disorder develops as a result of interactions between

  • biologically based vulnerabilities
  • early experiences with significant others, and
  • the role of social factors in buffering or intensifying problematic personality traits.

The overarching model – which includes work on attachment – is described in Figure 2.1 below.



Biological vulnerability includes the genetic and biological elements to personality development. Overall, about half the variation in personality characteristics is thought to be directly due to genetic differences between individuals. A summary of the evidence is detailed below.

  • There is considerable evidence for similarities in broad personality dimensions across all cultures.
  • Some personality traits are linked to particular biochemical markers in the brain; for example, impulsivity and emotional sensitivity.
  • It is well established that infants vary in basic temperament such as activity, sociability and emotional reactivity.

Biological vulnerability is particularly important in psychopathic individuals, where research has shown that some features of psychopathy seem to be related to anomalies in certain brain functions and structures, including some related to making moral decisions. This may well be one of the most important reasons to explain why psychopaths find it so difficult to change their behaviour.

Parental capacity and early experiences with significant others

At the core of this factor is the evidence for a biological human attachment behavioural system that brings a child close to its caretaker (usually mother or father). That is, early attachment behaviour in humans provides an evolutionary advantage for the survival of children who remain vulnerable and dependant on adults for relatively long periods of time. Attachment theory is at the core of our understanding of personality disorder, and is, therefore, explained in some detail in the section on attachment theory.

Social and cultural factors

The role of social factors in personality development is either to aggravate or to buffer against problematic characteristics in individuals. This accounts for much of the variation in types of personality problems across cultures and over time. For example, research has documented a reduction in the prevalence of antisocial personality disorder during times of war, and also in many Asian cultures. In both cases, the promotion of social cohesion, and an emphasis on the role of the community away from a focus on individuality, is likely to be a key factor.

The more local social context is also thought to provide a buffering effect, with employment, housing and social stability all playing a role.