Introduction to personality disorder evidence based treatments

By: Anthony Bateman and Mary Zanarini

The definition of personality disorder (PD) remains controversial. Both the DSM-IV and ICD-10 take a categorical approach to the diagnosis of PD defining different types of personality according to descriptive criteria. Tyrer et al. (1990), however, found little evidence that categories of personality disorder were helpful in determining response to treatment or indeed that they had any predictive value at all. Research orientated methods rely on structured and semi-structured interviewing or self-report screening measures. Although this improves reliability somewhat, the approach remains unsatisfactory (Pilkonis et al., 1995). Validity is questionable since the underlying construct, which determines diagnosis on Axis II of DSM, relies on self-reported styles of interpersonal function, self-assessment of personal traits, and declared impairment in social roles over a period of time.

Interviews utilize direct questions concerning habitual behavioural patterns and self-reported personality descriptions in a manner likely to heighten defensiveness and yield biased data. There is little emphasis on personality functioning in terms of key domains such as work, relationships and self-care (Hill et al., 1989), Developmental history is considered separately from diagnosis and response biases such as a plaintive response set and social desirability response bias have not been taken into consideration.

The clustering of specific trait-related personality disorders into three groupings is an attempt to address this lack of specificity of the diagnostic system. However, the three DSM-IV clusters (the odd-eccentric (Cluster A), the impulsive-erratic (Cluster B), and the anxious-avoidant (Cluster C)) have only face validity, as large cohort studies, which might confirm the stability of such groupings, have not been carried out. There are also indications that the North American and European systems of classification show insufficient levels of agreement (Sara et al., 1996).

The usefulness of this approach rests on its intuitive appeal to clinicians, which in its turn may have more to do with the relative ease with which category membership may be identified through the use of prototypes, than with the value of such a system in a scientific description of personality. Given the problems of diagnosis it will not come as a surprise to the reader to learn that this handicaps evaluation of treatments for personality disorder.

References

Peter Tyrer and Kenneth R. Silk, Cambridge Textbook of Effective Treatments in Psychiatry, Cambridge University Press 2008.

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