Categorical disease models of personality disorder currently dominate in the DSM-IV-TR and ICD-10 diagnostic systems. In preparation for DSM-V, these models have been questioned in light of evidence and widely held beliefs that disorders of personality are extreme variants of normal personality. Unfortunately, problems arise in trying to produce a dimensional model of abnormal and normal personality, such as how aspects of normal personality can he applied to personality disorders, and the all-important issue of precisely what aspect of normal personality is overextended in these disorders. In contrast to other approaches, a dimensional model based on defense mechanisms is easily applied to personality disorders, eliminates the need for complex scales, retains the notion of entities with which clinicians are familiar, provide useful therapeutic strategies, and clearly specify what aspect of normal personality is overextended. It also allows for the addition of new personality disorders.
KEYWORDS: personality; personality disorder; defense mechanisms; borderline personality disorder
Disorders of personality are widely believed to be extreme variants of normal personality rather than categorical diseases (Bernstein, Iscan & Maser, 2007). Current diagnostic methods represented by the DSM-IV-TR (First, Frances & Pincus, 2002) and ICD-IO (WHO, 2007), constitute categorical disease models. In preparation for DSM-V, efforts are being made to prepare a dimensional model that will have utility for clinicians. A major focus is to transform well-validated instruments for assessing the so-called normal personality into a dimensional model of abnormal personality (Mullins-Sweatt, Smit, Verheul, Oldham & Widiger, 2009).
While at first glance this approach seems logical and potentially illuminating, there are several major problems. One issue concerns how well dimensions of normal personality, as measured by these instruments can be applied to personality disorders. For example, how do extremes of one of the most well-established dimensions of normal personality, extroversion-introversion (Costa & McCrae, 1992) relate to disordered personality? Extreme extroversion might somewhat relate to histrionic personality disorder, but not fully, and extreme introversion might apply more to anxiety disorders than personality issues. Another common dimension of normal personality, responsiveness to the environment, does not produce any personality concern on the stability side. On the responsive side, extreme variants represent neuroticism, a personality type predisposing individuals to multiple mental health problems without specificity for a particular personality disorder. This same concern applies to virtually all dimensions of the normal personality.
A second problem concerns how to amalgamate normal personality measures into a tool for assessing abnormal personality. This approach blends personality dimensions from different normal personality assessment instruments. In some cases even the instrument scales are blended (Widiger & Simonsen, 2005). However, combining different personality dimensions from well-validated scales does not necessarily produce a valid and reliable instrument. There has to be extensive testing of any agreedupon instrument to establish its validity and reliability in both normal and abnormal personality settings because the dimensional approach must apply to everyone. This process may take years. Furthermore, the first problem, of how well aspects of normal personality apply to disordered personality, remains an obstacle.
The clinical utility of any process for assessing and rating abnormal personality is a third major obstacle in establishing a dimensional model of personality disorder (First, 2005; Verheul, 2006). Very few clinicians outside the research setting are likely to add a complex personality scale to their assessment processes, and this is particularly the case for psychiatrists, who are unaccustomed to using scales. …