Background: Dimensional models of personality are under consideration for integration into the next Diagnostic and Statistical Manual of Mental Disorders (DSM-5), but the clinical utility of such models is unclear.

Objective: To test the ability of clinical researchers who specialize in personality disorders to diagnose personality disorders using dimensional assessments and to compare those researchers’ ratings of clinical utility for a dimensional system versus for the DSM-IV.

Method: A sample of 73 researchers who had each published at least 3 (median = 15) articles on personal- ity disorders participated between December 2008 and January 2009. The Five-Factor Model (FFM), one of the most-studied dimensional models to date, was compared to the DSM-IV. Participants provided diagnoses for case profiles in DSM-IV and FFM formats and then rated the DSM-IV and FFM on 6 aspects of clinical utility.

Results: Overall, participants had difficulty identifying correct diagnoses from FFM profiles (t72 = 12.36, P < .01), and the same held true for a subset reporting equal familiarity with the DSM-IV and FFM (t23 = 6.96, P < .01). Participants rated the FFM as less clinically useful than the DSM for making prognoses, devising treatment plans, and communicating with professionals (all t69 > 2.19, all P < .05), but more useful for communicating with patients (t69 = 3.03, P < .01).

Conclusions: The results suggest that personality disorder expertise and familiarity with the FFM are insufficient to correctly diagnose personality disorders using FFM profiles. Because of ambiguity inherent in FFM profile descriptors, this insufficiency may prove unlikely to be attenuated with increased clinical familiarity with the FFM.