What is meant by the term personality disorder?
It is only possible to make meaningful statements about the epidemiology and management of a health problem, if an agreed definition of that problem exists. Unfortunately, health professionals do not agree about how best to define personality disorders, nor indeed whether the term personality disorder has any use at all. Despite over two decades of extensive research, psychiatrists and psychologists remain divided as to how these disorders should be conceptualised. Whilst a diagnosis of personality disorder can now be made reliably with a number of interview schedules, there is no consensus as to how to assess personality disorders. In addition, clinical and research methods for diagnosing personality disorders diverge and the level of agreement between schedules is generally very poor. Moreover, it is unclear how well clinical or research diagnoses actually capture the experiences of people identified as personality-disordered.
The World Health Organisation and the American Psychiatric Association have produced definitions of personality definitions. The International Classification of Mental and Behavioural Disorders (ICD-10) (World Health Organisation 1992), defines a personality disorder as: ‘a severe disturbance in the characterological condition and behavioural tendencies of the individual, usually involving several areas of the personality, and nearly always associated with considerable personal and social disruption’. The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (American Psychiatric Association 1994) defines a personality disorder as: ‘an enduring pattern of inner experience and behaviour that deviates markedly from the expectations of the individual’s culture’.
There are nine categories of ICD-10 personality disorder and ten categories of DSM-IV personality disorder. The classification scheme is unwieldy as personality-disordered patients rarely belong to just one category of personality disorder. A solution to this problem and one that has been shown to be useful in distinguishing different populations of psychiatric patients, is the DSM clustering system (Reich & Thompson 1987). (The clustering system also better reflects the scientific evidence surrounding abnormal personality as it effectively hybridises dimensional and categorical models of personality disturbance). This system groups the subcategories of DSM-IV personality disorder into three broad groups or ‘clusters’ of personality disorder:
- Cluster A (the ‘odd or eccentric’ types): paranoid, schizoid and schizotypal personality disorder
- Cluster B (the ‘dramatic, emotional or erratic’ types): histrionic, narcissistic, antisocial and borderline personality disorders
- Cluster C (the ‘anxious and fearful’ types): obsessive-compulsive, avoidant and dependent.
The area of personality disorders is already over-burdened with confusion and in order to avoid exacerbating this, health professionals should stick to the current ICD and DSM definitions of the term personality disorder. The advantage of using these definitions is that they have been agreed upon by large international groups of psychiatrists and psychologists, and a large epidemiological evidence base (summarised in this chapter) supports their use. However, for the reasons outlined above, the definitions have limitations. Clinicians and researchers working in collaboration with users should therefore strive to refine the definitions we already have at our disposal.
The remainder of this chapter summarises the research dealing with the prevalence and burden associated with personality disorders. The research evidence is based on ICD and DSM concepts of personality disorder.
Section I: How common are personality disorders?
How common are personality disorders in the community?
Community studies of the prevalence of unspecified personality disorder report prevalence figures ranging from 10-13% (de Girolamo & Dotto, 2000). These studies have found that personality disorders are more common in younger age groups (particularly the 25-44 year age group) and equally distributed between males and females. (N.B. This is for all personality disorders. The sex ratio for specific types of personality disorder is variable e.g. antisocial PD is commoner among males). At a community level, personality disordered individuals are more likely to suffer from alcohol and drug problems. In addition, they are also more likely to experience adverse life events, such as relationship difficulties, housing problems and long-term unemployment. The most consistently studied personality disorder in community studies has been antisocial personality disorder, which has a lifetime prevalence of between 2 and 3%, and is commoner in men, younger people, those of low socio-economic status, single individuals, the poorly educated and those living in urban areas (Moran 1999). There are almost no community data on other personality disorders from countries other than the United States, the United Kingdom, Germany and Australia.
How common are personality disorders in primary care?
Our knowledge about the prevalence of personality disorders in primary care is derived from two sources: routine data (as collected by GPs) and epidemiological studies. In 1995, the consultation rate (per 10,000 person years at risk) for personality disorder was 32, in England and Wales. This compares with 280 for depressive disorder and 707 for neurotic disorders (McCormick et al, 1995). Based on these GP statistics alone, personality disorders (as the main reason for consulting) do not seem to be contributing greatly to the workload of GPs. Nevertheless, epidemiological studies report that the prevalence of personality disorder in primary care lies between 10 and 30% (Dilling et al, 1989; Casey & Tyrer 1990). The highest prevalence occurs among GP patients with conspicuous psychiatric illness, although this may be due to abnormalities of mental state biasing the assessment of personality. Patients with Cluster C personality disorders are the commonest personality disorders to be encountered among primary care attenders (Moran et al, 2000), although in their clinical practice, GPs encounter the whole range of personality disorders.
How common are personality disorders in secondary care?
Personality disorders are frequently encountered in populations of psychiatric patients, either as the main psychiatric condition, or as ancillary conditions, where they colour the presentation and treatment of mental illness. Numerous studies have examined the prevalence of personality disorders in psychiatric hospital populations and report a wide range of prevalence estimates. (For a recent review of this area, please see de Girolamo & Dotto (2000). The findings from a selection of international studies are displayed in the Table (see Appendix). It is difficult to draw definitive conclusions from the large number of psychiatric studies carried out because of differences in sampling, diagnostic criteria and assessment methods. Nevertheless, certain generalisations can be made:
· In general, the prevalence of personality disorders among psychiatric outpatients and inpatients is high, with many studies reporting a prevalence of greater than 50% of samples.
· Borderline PD is generally the most prevalent (and certainly most heavily researched) category in psychiatric settings.
· Personality disorders are particularly prevalent among inpatients with drug, alcohol, and eating disorders. In these populations, prevalence figures for personality disorder have been reported to be in excess of 70%.
- Generally, patients meeting criteria for one category of personality disorder also meet the criteria for other personality disorders. However, it is not clear whether this indicates the true concurrence of discrete personality disorder categories, or merely represents the failure to define disorders precisely i.e. a problem with diagnostic validity. This provides one of the strongest pieces of evidence against our present classification system for personality disorders.
- With regard to comorbidity between personality disorders and other mental disorders, the most heavily studied patterns are between personality disorders and: substance abuse, anxiety disorders and affective disorders. Whilst certain patterns of Axis I – Axis II comorbidity appear to be relatively strong and probably represent ‘true concurrence’ (e.g. somatisation disorder with Cluster C personality disorders), the validity of other associations is more questionable (e.g. antisocial PD with substance abuse) and may be an artefact created by overlapping diagnostic criteria.
In psychiatric settings, people with Cluster B personality disorders (almost by definition) attract the most attention. People with Cluster B personality disorders share the characteristic of poor impulse control and often present to hospital services in crisis, threatening deliberate self harm, aggression to others or when intoxicated. A scarcity of in-patient beds combined with the fact that personality-disordered patients are difficult to manage has led to an increasing reluctance to admit such patients to hospital. However, research has shown that brief time-limited admissions to hospital may in fact benefit some personality-disordered patients in crisis. In a randomised controlled trial of one hundred psychiatric emergency cases allocated to community or hospital-based services, patients with personality disorders (50% of the patient group) showed greater improvement in depressive symptoms and social functioning when referred to the hospital-based service (Tyrer et al, 1994).
How common are personality disorders in prisons?
The accurate determination of the prevalence of personality disorders in prisons is particularly problematic. The diagnostic criteria for antisocial personality disorder include law-breaking behaviour, which means that this particular personality disorder category overlaps greatly with criminality. It is also the most prevalent category of personality disorder in prison settings. A survey of a randomly selected sample of one in six prisoners in England and Wales, found that the prevalence of any personality disorder was 78% for male remand, 64% for male sentenced and 50% for female prisoners (Singleton et al, 1998). Antisocial personality disorder had the highest prevalence of any category of personality disorder, with 63% of male remand prisoners, 49% of sentenced prisoners and 31% of female prisoners. Such high prevalence estimates raise important questions about the validity of the diagnosis and the medicalisation of criminality. In an attempt to overcome the reliance on criminal behaviour for diagnosing personality disorder, some researchers have focused on underlying abnormal personality traits associated with ‘psychopathy’ such as callousness and lack of empathy. Nevertheless, it is unclear how useful the concept of psychopathy is outside of forensic settings
Section II: The burden of personality disorders
Personality disorders are associated with a significant burden to the individual, those around them and society as a whole. However, personality disorders are defined in terms of their associated handicap and this leads to circularity in their definition. This is best exemplified by antisocial personality disorder – the definition specifically emphasises antisocial behaviour, therefore, populations of criminals usually have a very high prevalence of antisocial PD. Despite these semantic imperfections, a great deal of research has been conducted into the social impact of personality disorders.
Suicide and deliberate self-harm
Personality disorders are associated with suicidal behaviour, although the magnitude of risk varies considerably between specific categories of disorder. A number of studies, have examined the nature of this association using case-control and cohort designs. Using a psychological autopsy method and a case-control design, Lesage et al, (1994), examined the association between mental disorder and suicide among a group of young men from Canada. At least one axis I disorder was identified in 88% of suicide subjects (OR: 12.3; 95% CI: 5.3 – 28.5) and at least one axis II disorder was identified in 57% of suicide subjects (OR: 4; 95% CI: 2 – 7.9). The commonest axis II disorders were borderline (OR: 9.3; 95% CI: 2.6 – 33) and antisocial personality disorders (OR: 4.1; 95% CI: 1 – 15.4). Using a biographical reconstructive interview conducted for consecutive suicides from three ethnic groups in East Taiwan, Cheng et al, (1997) found that between 47% and 77% of suicides suffered from ICD-10 personality disorder. In all groups, the most prevalent category among suicides was emotionally unstable personality disorder, occurring in 41% of suicides (OR: 9.9; 95% CI: 4.6 – 21.1). Harris & Barraclough (1997) conducted a meta-analysis of the published literature on mental disorders and suicide. They focused on cohort studies, with a follow-up of at least two years, with less than 10% attrition rate at follow-up. Virtually all mental disorders were associated with an increased risk of suicide. The authors identified five papers reporting on a population of over 3,000, which examined the prospective association between personality disorders and suicide. The standardised mortality ratio for personality disorders from these cohort studies was 708 (95% CI: 477-1010).
The association between personality disorders and deliberate self-harm (DSH) is complicated by the fact that DSH is one of the diagnostic features of borderline and impulsive personality disorders. Nevertheless, some studies have also demonstrated an association between DSH and other personality disorders. Dyck et al (1988) examined the lifetime histories of attempted suicide and psychiatric disorders on a random sample of 3,258 household residents of Edmonton, Canada. Approximately 80% of those with a history of suicide attempts had a lifetime psychiatric disorder. The greatest relative risks were associated with schizophrenia (23.1) and mania (21.0). The relative risk of attempting suicide given a diagnosis of antisocial personality disorder was 4.0. Beautrais et al (1996) adopted a case-control design in order to examine the association between mental disorders and attempted suicide. 302 consecutive subjects who made serious suicide attempts were compared with 1,028 randomly selected controls. Of those who attempted suicide, 90% had a mental disorder at the time of the attempt. The odds of a serious suicide attempt were significantly higher for individuals with a diagnosis of mood disorder (OR: 33.4; 95% CI: 21.9 – 51.2); substance use disorder (OR: 2.6; 95% CI: 1.6 – 4.3); or antisocial personality disorder (OR: 3.7; 95% CI: 2.1 – 6.5).
Mortality and accidents
Because some personality-disordered people engage in impulsive and dangerous behaviour, they have an elevated mortality rate. In a 6 – 12 year prospective follow-up of 500 psychiatric outpatients, Martin et al (1985) found that a diagnosis of antisocial personality disorder (ASPD) was associated with a significant excess of unnatural causes of death (largely suicide, accidents and homicides). In the reference population, the standardised mortality ratio for unnatural deaths was 4.3. In addition, retrospective data confirms that ASPD is a risk factor for both sudden violent death (Rydelius, 1988) and accidental injury (McDonald & Davey, 1996). ASPD has also been found to be associated with HIV risk-taking behaviour (Brooner et al, 1993).
Evidence for the existence of an association between personality disorders and violence comes almost exclusively from cross-sectional studies of the prevalence of personality disorders among people who have committed violent acts. Thus, the prevalence of personality disorder has been found to be high among homicide offenders (Eronen et al, 1996), high security hospital patients (Taylor et al, 1998), and men who batter their wives (Dinwiddie 1992). The problem with interpreting findings from these studies is that they are susceptible to selection bias and also do not allow examination of the temporal relationship between personality disorder and violent behaviour. However, there has been little longitudinal research examining the association between personality disorders and violence. It is worth noting that the validity of the recent proposals on ‘dangerous severe personality disorder’ rests on the assumption that there is a robust association between violence and personality disorder.
The prevalence of certain categories of personality disorder is high among sentenced and remand prisoners. Nevertheless, the association between ASPD and criminal behaviour in large part reflects the fact that criminal behaviour is one of the diagnostic criteria for ASPD. In addition, there have been very few longitudinal studies of the association between personality disorder and offending behaviour. Hodgins et al (1996) used Danish registries to identify a birth cohort and to document all psychiatric admissions and all criminal proceedings of the 324,401 members of this cohort up to age 43 years. For both men and women, having any psychiatric diagnosis significantly increased risk for all types of crime. For the period 1978 – 1990, the estimated relative risk of committing a crime given a diagnosis of ASPD was 6.5 (95% CI: 5.9 – 7.1) for female subjects and 5.3 (95% CI: 5.0 – 5.6) for male subjects. The estimated relative risk for registering for at least one violent crime was 12.2 (95% CI: 8.8 – 16.9) for female ASPD participants and 7.2 (95% CI: 6.5 – 8.0) for male ASPD participants.
Associated mental illness
People with personality disorders are more likely to also suffer from other psychiatric problems during their lifetime. In particular, they are more likely to suffer from depression; (Corruble et al, 1996), anxiety disorders (Tyrer et al, 1983; Sanderson et al, 1994), and substance abuse and dependence (Robins 1998). The association between psychiatric illness and personality disorders is however complicated by the fact that:
- The presence of a psychiatric illness may bias the assessment of personality leading to an erroneous diagnosis of personality disorder.
- Diagnostic criteria for some personality disorders and some psychiatric illnesses overlap, resulting in ‘false comorbidity’. This is a particular problem for the following associations: avoidant personality disorder and social phobia, substance use disorders and antisocial personality disorder, and borderline personality disorder and post-traumatic stress disorder.
The presence of personality disorder can have an unfavourable impact on the outcome of the treatment of associated psychiatric illness. In terms of common mental disorders, such as depression and anxiety, early research suggested that the presence of a personality disorder was almost invariably associated with a poorer response to treatment for the mental illness (Reich & Green 1991). More recent reviews of this area indicate that the effect of personality disorder on treatment is more complex and may depend on the type of treatment, the type of personality disorder, the length of follow-up and the type of study design employed (Dreessen & Arntz 1998); (Mulder 2002). Data from the UK700 trial indicate that personality status has a substantial negative impact on a number of prospective clinical outcomes for schizophrenia (Tyrer & Seivewright, 2000). Numerous studies report a strong association between the Cluster B personality disorders and drug and alcohol dependence. Early research indicated that personality disorders were associated with a poorer treatment outcome (Woody et al. 1985). However, more recent studies have shown that the effect of personality disorder on treatment outcome for addiction is more variable (Darke, et al 1994; Hoffman et al. 1994).
Health service utilisation
Studies of health service utilisation patterns indicate that individuals with personality disorders are frequent users of health services at both the level of primary care and secondary care. In primary care, personality disordered attenders are more likely to be frequent attenders to general practice (Moran et al, 2001), to consume psychotropic medication excessively (Seivewright et al, 1991), and to engage in difficult consulting behaviour (Hahn et al, 1996). At the level of secondary care, people with cluster B personality disorders have been shown to heavily use psychiatric services (Perry et al, 1987; Narrow et al, 1993). American data from the ‘Collaborative Longitudinal Personality Disorders Study’ has shown that treatment-seeking patients with borderline personality disorder report greater use of psychiatric medication, hospitalisation, psychotherapy, day care and social care compared to patients with major depressive disorder (Bender et al, 2001). In addition, prospective research has identified personality disorder as a significant predictor of repeated episodes of psychiatric hospitalisation, or the ‘revolving door syndrome’ (Saarento et al, 1998).
The economic impact of personality disorders on the health service remains largely unexplored. In a cost-of-illness study that used UK national prevalence data, and data on service usage, Smith et al (1995) estimated that in 1986, the NHS spent £61.24 million on personality disorders. This figure was over four times that spent on substance and alcohol misuse. Rendu et al (2002) followed-up 303 general practice attenders one year after they had been assessed for the presence of personality disorders. The mean total cost (health and non-health costs) for personality-disordered patients was £3094 (SD = 5324) compared to £1633 (SD = 3779) for non personality-disordered patients.
The impact of specialist treatment on health service costs by patients with personality disorder has not yet been fully examined. In a prospective study comparing patterns of health service use by three groups of people with personality disorder Chiesa et al, (2002) found that a ‘step-down’ program of specialist treatment produced greater savings in health service costs compared to both a hospital-based and a general psychiatric program.
Despite the emergence of ICD and DSM definitions of personality disorder, there is lack of agreement about whether these definitions are helpful. Neverthless, the definitions are the best ones we have and a substantial body of epidemiological data has emerged over the past twenty years supporting their use. In the interests of improving our knowledge about personality problems, clinicians and researchers, working in collaboration with users, must achieve greater consensus about what is meant by the term personality disorder.
Personality disorders (as defined by ICD and DSM) are common conditions. Their prevalence steadily increases with each level of care and they are therefore frequently encountered in clinical practice. Epidemiological surveys suggest that personality disorders are most prevalent in the setting of prisons, although this may merely reflect the fact that criminal behaviour is one of the diagnostic features of antisocial personality disorder (the most prevalent category of personality disorder in prisons). In general adult psychiatric teams, Cluster B personality disorders attract the greatest attention, although we know little about their prevalence among patients routinely seen by community mental health teams. The present fuss surrounding Cluster B disorders should not obscure the fact that in their clinical practice, mental health professionals encounter people with a wide range of personality-related problems.
The broad group of personality disorders is associated with a multitude of health and social problems. However, in part, this reflects the circularity in their definition – they are defined in terms of their associated handicap. Significant gaps exist in our knowledge about the longitudinal course of personality disorders. Perhaps one of the most conspicuous gaps, in the light of recent government proposals, is the paucity of robust evidence for the association between personality disorders and violent behaviour.
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Table 1. Selection of international studies of personality disorder in samples of psychiatric patients
|Alnaes & Torgersen (1988)
|Norway||298 consecutive outpatients||Prevalence of DSM-III PD:
|Pilgrim & Mann (1990)
|UK||120 consecutive new admissions||Prevalence of ICD-10 PD: 36%|
|Jackson et al (1991)
|Australia||112 inpatients with severe mental illness||Prevalence of DSM-III PD: 67%|
|DeJong et al (1993)
|Holland||178 inpatient alcoholics + 86 polydrug addicts||Prevalence of DSM-III PD:
Alcohol group: 78%
Polydrug group: 91%
|Braun, et al (1994)
|USA||105 consecutive inpatients to an eating disorders unit
|Prevalence of DSM-III PD:
|Sato et al (1999)
|Japan||118 consecutive outpatients with depression
|Prevalence of DSM-III-R PD: