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Dimensional models may obscure important diagnostic differences.

Borderline and antisocial personality disorders demonstrate strong diagnostic validity.

Fuzzy boundaries do not negate real clinical syndromes.

In recent years, 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

One of the enduring problems with the DSM system is that it implicitly treats all diagnoses as equally valid or "real." Thus, schizophrenia, bipolar disorder, and obsessive compulsive disorder are placed alongside far more weakly validated conditions as if all represent the same degree of empirical support (Ghaemi & Ruffalo, 2026).

When it comes to personality disorders, two diagnoses........

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