Everyone has personality traits that characterise them as unique individuals. Such traits refer to the usual way in which a person thinks, feels and behaves. Specifically, personality refers to the pattern of thoughts, feelings and behaviours, consistently exhibited by an individual over a long period of time. Personality is a complex combination of traits and characteristics that determines our expectations, self-perceptions, values and attitudes, and predicts our reactions to people, problems and stress. Personality is not just who we are, it is also how we are.

We all have personality traits and characteristics that appear distinct and unique. A major characteristic of these personality traits and characteristics is in their ingrained quality. That is, they are deeply rooted and firmly established in an individual’s character. The degree to which we exhibit a specific personality trait varies from person to person.

Some personality traits have biological roots, but all are influenced by our environment, especially our family relationships. Consequently, the millions of possible combinations of personality traits, in varying degrees, accounts for the unique individuality we all possess, but the relatively small number of different personality traits also explain why there are so many similarities between groups of people.

Possession of a personality trait that is typically found in the criteria for a personality disorder does not show as evidence of a personality disorder. It is only when personality traits are inflexible and maladaptive and cause significant functional impairment or subjective distress that they are most likely to constitute as being a personality disorder. A personality disorder refers to a pattern of thoughts, feelings and behaviours that are consistently exhibited by an individual over a long period of time and are maladaptive because they create psychological distress and life coping problems, rather than assisting the individual with life adjustment and problem solving.

The DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition) defines a personality disorder as “an enduring pattern of inner experience and behaviour that deviates markedly from the expectations of the individual’s culture, is pervasive and inflexible, has an onset in adolescence or early adulthood, is stable over time, and leads to distress and impairment” (APA, 2000). So diagnosis of a personality disorder is only made when an individual’s personality characteristics are inflexible and maladaptive and cause significant impairment or subjective distress (Barlow & Durand, 2009).

Personality disorders do not typically stem from debilitating reactions to stress in the recent past as do other cases of mental disorders. Rather, these disorders develop from the gradual development of inflexible and distorted personality and behavioural patterns that result in persistently maladaptive ways of perceiving, thinking, feeling, behaving and relating to the world (Butcher, Mineka & Hooley, 2009).

Personality disorders are mixed in their clinical features and aetiology. Their symptom complexities are caused by combinations of hereditary temperamental traits, environmental factors and developmental events. The relative percentages of genetic and environmental factors vary with each specific personality disorder. The treatment of other psychiatric disorders becomes far more complicated in clients who have such disorders in comorbidity with personality disorders.