Personality disorder (previously referred to as character disorder) is a fairly modern form of diagnosis, and is seen as an intrinsic part of the personality, rather than an illness as such.

There are actually ten different diagnoses of personality disorders, including the most common, by far, Borderline Personality Disorder.

The definition of personality disorder is very subjective, and is largely based on people having an inner world, and thus behaving differently from the expectations of the society in which they live. People with personality disorders can have difficulties in relationships, in coping with stress, in a variety of different ways, and can become very isolated.

A problem, historically, is that because personality disorders are not very amenable to treatment by drugs, there has been a difficulty in forming treatments, or getting treatment for personality disorders under psychiatric services.

Recent theories of attachment and brain development are throwing new light on the formation of personality disorders, and are giving rise to a number of different therapies which are gradually emerging, and there are some specific CBT (Cognitive Behavioural Therapy) interventions.

Also, due to the isolation which is often inherent in the lives of people who have acute difficulties in relating, there are often other 'co-morbid' (difficulties alongside) mental health problems, such as depression, anxiety, and drug or alcohol misuse.