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Personality disorder

Another issue that the inquiry has been looking at is the treatment of people with personality disorder in the criminal justice system.

Most people with personality disorder are not involved in the criminal justice system. However, studies have found that 50-78% of adult prisoners are believed to meet criteria for one or more personality disorders, and even higher prevalence estimates have been reported among young offenders.[1] The treatment and understanding of personality disorder is therefore an issue of overwhelming significance for the criminal justice system in general and prison in particular.

What is personality disorder?

Personality disorder has been defined as persistent and inflexible personality attributes that vary markedly from the expectations of the individual’s culture and that lead to distress or impairment.[2]

The concept of personality disorder is therefore made up of two elements:

(a)   deviation from a cultural or social norm;

(b)   adverse consequences of that deviation.

Inevitably, social values and prejudices affect both (a) the definition of what is extreme or abnormal and (b) the extent to which such abnormal traits can be described as adverse.

Some people may have extreme personality traits but function adequately because their characteristics are not an impediment for a particular role or setting. For instance, people in positions of power may have extreme personality traits that go unchallenged. As a result, they may not suffer distress or impairment and the effect on others may remain hidden. Such cases would not be classified as a disorder. People with a high socio-economic status are also more likely to have the means to adapt their environment in order to mitigate the worst effects of their personality characteristics.

By contrast, those from poor and disadvantaged backgrounds are more likely to be in roles and settings where there is a narrower range of tolerance for extreme personality traits. They are also likely to have a narrower range of options available to them to mitigate the effects of such traits.

This is likely to be one reason why the majority of studies of the community prevalence of antisocial personality disorder indicate a clear link with low socioeconomic status.[3] Antisocial personality disorder has been found to be the most common specific diagnosis in both male and female prisoners, although it was found to be more prevalent in men (63 per cent of remand and 49 per cent of sentenced males) than women (31 per cent of female prisoners).[4]  

In this context it is also worth noting that clinicians have been found to diagnose men with antisocial personality disorder and women with borderline personality disorder on the basis of identical descriptions.[5] This again reflects differences in the ways personality traits are valued and either challenged or accepted in different social roles and settings.

Other factors that have been said to play a role in the development of personality disorder are genetics, temperament, brain function and biochemistry, childhood neglect, abuse and trauma and family and parental influences. There is a considerable overlap between these factors. It is thought that no single factor is sufficient to produce personality disorder and that only multiple adverse life experiences will do so.[6]

Person versus situation

Psychologists used to disagree on the usefulness of the idea of personality. Some argued that behaviour has more to do with the situations in which people find themselves than with stable characteristics. This debate has now been replaced by a consensus among psychologists that behaviour depends on the characteristics of both the person and the situation.[7]


The most commonly recognised criteria for diagnosing personality disorder are set out in the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, fourth edition) published by the American Psychiatric Association. This uses a model based on fixed categories, implying a qualitative difference between normality and abnormality. An alternative approach is a dimensional approach that sees personality as a spectrum and looks at differences of degree in its function.


It is commonly said that there is a weak evidence base for the treatment of personality disorder. Neither medication nor talking therapies, whether in the community or in in-patient settings, have yet been found to have a significant long-term impact on people with personality disorder.

There have been few studies and the number of patients involved has been low. This is complicated by the use of multiple outcomes, with few in common between studies, and by the fact that people do not have to meet all of the criteria for each personality disorder to qualify for a diagnosis. This means that there can be big differences between people with the same diagnosis.  

There may also be a problem with how outcomes are defined and with the theoretical model of what is ‘wrong’ with the person that the treatment implies.[8]                           

For borderline personality disorder, such evidence as there is suggests that long-term structured and theoretically integrated psychological therapy programmes, with other inputs and access to support between sessions, are more effective than isolated and/or short-term individual psychological therapies.

The evidence base for treatment is summarised in two guidelines from the National Institute for Health and Clinical Excellence, one on anti-social personality disorder (NICE guidance 99 2009) and one on borderline personality disorder (NICE guidance 78 2009).

Non-treatment based approaches

While many people with personality disorder experience considerable difficulties coping with life and desperately want help, others do not wish to change or do not feel that the treatment on offer is right for them. Some may want or feel able to change some aspects of their problems but not others.

Such responses may be common in prisons and secure hospitals. The fact that the person has not chosen to be there can impact on the ‘therapeutic alliance’ with treating staff, which is considered to be an important part of treatment.

This has led to some people with personality disorder being labelled ‘treatment-resistant’. For such people, some researchers and clinicians have advocated a different approach based on the acceptance of a level of disability and the provision of environmental or other adjustments, such as social and vocational rehabilitation, aimed at managing and mitigating its effects.

An example of this approach is nidotherapy, from the Latin, nidus, or nest, a type of natural environment that adapts to its user. Nidotherapy does not attempt to change the person but instead manipulates the environment in order to create a better fit with the person. It involves seeing the environment from the person’s point of view and formulating realistic environmental targets in agreement with them.[9]

Prison is a highly inflexible and maladaptive environment and its use is the opposite of the nidotherapeutic approach.

Nidotherapy was developed in the context of assertive community outreach teams and its application to forensic secure settings has not yet been fully explored.

The level of environmental change that is possible in any given case will be limited, particularly in a secure setting. However, this will be less so where it is accepted as a strategy by those involved in the person’s care. 


[1] Understanding Personality Disorder, a report by the British Psychological Society, February 2006

[2] DSM-IV-TR, American Psychiatric Association, 2010

[3] Understanding Personality Disorder, citing 1998 study by Kohn, Dohrenwend & Mirotznik. The report notes that the only other personality disorders considered in this context suggest that obsessive-compulsive personality disorder is significantly more prevalent in higher socioeconomic groups.

[4] Office for National Statistics Study on Psychiatric Morbidity among Prisoners (Singleton et al., 1998).

[5] Adler et al., 1990, cited in BPS report

[6] Understanding Personality Disorder, a report by the British Psychological Society, February 2006

[7] BPS report, p.4

[8] NICE guidance on anti-social personality disorder, p.33; NICE guidance on borderline personality disorder, p.102

[9] Nidotherapy: making the environment do the therapeutic work, Tyrer P. and Bajaj P., Advances in Psychiatric Treatment (2005), Vol 11, pp.232-238