Can ICD-11 Personality Disorder Trait Dimensions Be Categorically Specified?

The new ICD-11 Personality Disorder (PD) classification introduces a global severity classification (i.e., mild, moderate, and severe) of personality dysfunction, which may be further accompanied by up to five trait domain specifiers delineating individual manifestations of personality disturbance (i.e., Negative affectivity, Detachment, Dissociality, Disinhibition, and Anankastia). Although these trait domains are conceptualized as dimensions, the ICD-11 only allows clinicians to code them as being categorically present versus absent. It is therefore appropriate to examine the ability of clinicians' judgements in capturing variance in trait domains using dichotomous trait ratings. A total sample of 238 patients was characterized by their clinicians using both dimensional and dichotomous single-item ratings for each trait domain. Subsequently, clinicians filled out the Informant Personality Inventory for ICD-11 (IPiC) as a standardized criterion-measure for trait domains. The dichotomous ratings were all moderately associated with their corresponding IPiC score, except for Negative Affectivity, which only showed a small but statistically significant association. The dimensional ratings were all moderately to strongly associated with their corresponding IPiC scores. However, only the dimensional single-item ratings of Disinhibition and Dissociality were significantly superior to the dichotomous single-item ratings in capturing the IPiC trait domain scores. Findings overall support the use of categorical assignment of trait domain specifiers in the ICD-11 although dimensional formats improve the accuracy of clinicians' judgements.