Does DSM-IV already capture the dimensional nature of personality disorders?

Personality disorder research favors a dimensional representation of the personality disorders over categorical classification, and this is one of the central justifications for changing the diagnostic approach in DSM-5. However, recent research has suggested that the most important loss of information in a categorical system is the failure to account for subthreshold levels of pathology. DSM-IV can be considered to already accommodate a quasi-dimensional system insofar as individuals who do not meet the threshold for diagnosis can be noted to have traits of the disorder. In the present report, we examined 2 questions related to dimensional scoring of the personality disorders and the association between personality pathology and psychosocial morbidity: (1) Is the DSM-IV 3-point dimensional convention (absent, subthreshold traits, present) more strongly associated with indicators of psychosocial morbidity than a categorical approach toward diagnosis? and (2) How does the 3-point dimensional scoring convention compare to the 5-point system proposed for DSM-5 and to a criterion count approach in which the dimensional score represents the sum of the number of criteria present?

From September 1997 to June 2008, 2,150 psychiatric outpatients were evaluated with semistructured diagnostic interviews for DSM-IV Axis I and Axis II disorders and measures of psychosocial morbidity.

The DSM-IV 3-point dimensional convention was more strongly associated with measures of psychosocial morbidity than was categorical diagnosis. There was no difference between the 3-point, 5-point, and criterion count methods of scoring the DSM-IV personality disorder dimensions.

Dimensional scoring of the DSM-IV personality disorders was more highly correlated with measures of psychosocial morbidity than was categorical classification. The DSM-IV 3-point rating convention was as valid as scoring methods using more finely graded levels of severity. These findings argue against changing the current DSM-IV diagnostic approach and instead advocate for the increased recognition that DSM-IV already includes a valid dimensional rating.