Since the questionnaire relies on client self-report, all responses should be verified by the clinician, and a definitive diagnosis is made on clinical grounds taking into account how well the client understood the questionnaire, as well as other relevant information from the client.
Statistically speaking, in a mixed-diagnosis outpatient psychiatric sample, 99% of the time a patient’s Z score will fall between -3 and +3, and the average Z score will be 0. Practically speaking, a Z score near or above the Z score listed for a diagnostic group is likely to be diagnostically suggestive and clinically meaningful. However, please keep in mind the following:
(1) The PBQ assesses beliefs associated with various Axis II disorders. It does not directly assess the criterion behaviors for these disorders.
(2) Assessment of criterion behaviors should be done through other assessment methods (e.g., diagnostic interviewing).
(3) There is no empirically established cut-off score on the PBQ that indicates the presence or absence of a personality disorder diagnosis.
Cognitive theory of personality disorders emphasizes the importance of schemas and core beliefs as organizational structures and global mental representations that guide information processing and behavior (Beck, Freeman, Davis, & Associates, 2003). Research over the past decade has identified specific sets of dysfunctional beliefs that are empirically associated with the various Axis II personality disorders (Beck, Butler, Brown, Dahlsgaard, Newman, & Beck, 2001; Butler, Brown, Beck, & Grisham, 2002). Being cognizant of the prototypic cognitive profile of each personality disorder can help guide clinicians as they conceptualize difficult cases.
Personality disorder beliefs have been measured using the Personality Belief Questionnaire (Beck and Beck, 1991). Beck et al. (2001) recently examined the criterion validity of the PBQ Avoidant, Dependent, Obsessive-Compulsive, Narcissistic, and Paranoid scales among psychiatric outpatients with corresponding SCID-II-derived diagnoses. Findings strongly supported the study predictions. In general, patients with one of these Axis II diagnoses scored higher on the corresponding PBQ scale than patients with alternative Axis II diagnoses. Also, patients scored significantly higher on the PBQ scale theoretically associated with their Axis II diagnosis than on PBQ scales associated with other personality disorders. A subsequent study conducted by Butler et al. (2002) identified 14 PBQ beliefs that empirically distinguish patients with borderline personality disorder from patients with other personality disorders.
The PBQ can be used clinically in two ways: to provide a cognitive profile and to identify specific dysfunctional beliefs that can be addressed in treatment. One benefit of a PBQ profile is that the relative strengths of beliefs across numerous personality disorders can be seen. This is important since personality disorder patients rarely present with a “pure” personality disorder and co-existing features from multiple personality disorders are common (Clark, 1999). PBQ responses can be reviewed with patients to explore several important areas: for example, how certain beliefs are currently impacting their emotions and behavior and how these beliefs may have been learned and maintained, even in the face of significant contradictory data. Patients can also be guided to assess the relative advantages and disadvantages of holding these beliefs and to develop alternative more adaptive beliefs.
