The Limits of Dimensional Models of Personality Disorder

"Dimensional models of personality disorder have become increasingly influential, particularly among trait psychologists and personality researchers. Two prominent examples are the ICD-11 personality disorder framework and the Alternative Model for Personality Disorders (AMPD) included in the appendix of DSM-5. Although these models differ in important ways, they share the assumption that personality pathology is best understood dimensionally rather than as a set of distinct disorders. According to this view, conditions such as borderline, narcissistic, and antisocial personality disorder reflect different configurations of maladaptive traits and severity rather than fundamentally separate syndromes."

"Although the AMPD retains the traditional personality disorder categories alongside dimensional trait ratings, this hybrid structure was largely a compromise designed to ease the transition away from the categorical model (see Gunderson, 2013). Many proponents of dimensional approaches ultimately favor a fully dimensional system in which the existing categories are substantially deemphasized or abandoned altogether."

"I wish here to raise three objections to dimensional models of personality disorder. 1. Dimensional models do not account for differences in diagnostic validity between personality disorders. 2. Borderline and antisocial personality disorders demonstrate strong diagnostic validity. 3. Fuzzy boundaries do not negate real clinical syndromes."

Dimensional models of personality disorder have gained influence, including ICD-11 and the DSM-5 AMPD. These frameworks assume personality pathology is best understood dimensionally, with disorders reflecting configurations and severity of maladaptive traits rather than fundamentally separate syndromes. The AMPD keeps traditional categories while adding dimensional trait ratings, largely to ease transition from categorical diagnosis. Objections include that dimensional models may treat all diagnoses as equally real despite differences in diagnostic validity. The argument notes that some personality disorders have stronger empirical support than others. Borderline and antisocial personality disorders are presented as having strong diagnostic validity, and fuzzy boundaries are said not to negate real clinical syndromes.

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