The American Psychiatric Association in the Diagnostic and Statistical Manual (DSM) of Mental Disorders, revised 4th edition (DSM IV-R) defines personality disorders 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 onset in adolescence or early childhood, is stable over time and leads to distress or impairment.” They are collectively known as the “axis 2” disorders in the current DSM classification.

The point at which personalityproblems become personality disorders is generally taken as the point at which the personality disturbance results in reduced personal, social and occupational functioning, as well as impaired relationships.

Factors important in the development of personality disorders are both environmental and physical. Environmental factors include adverse childhood experience, for example abuse, neglect and trauma, leading to problems in maintaining relationships in later life; physical factors include genetic predisposition and abnormal neurochemical metabolism. They frequently co-exist with ‘axis 1’ disorders and modify the presentation of other mental illnesses.

DSM IV-R divides personality disorders into three clusters:

Cluster A

The ‘odd and eccentric’ group

Paranoid

Schizoid

Schizotypal

Cluster B

The ‘flamboyant or dramatic’ group

Antisocial

Borderline (called ‘emotionally unstable’ in other classifications)

Histrionic

Narcissistic

Cluster C

The ‘anxious and fearful’ group

Avoidant

Dependent

Obsessive compulsive

Prevalence

In Britain, the prevalence of personality disorders ranges from 2% to 13% in the general population. Personality disorders are more common in institutional settings such as hospitals, prisons and residential homes and in people suffering from alcohol or substance misuse and eating disorders.

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