BACKGROUND: Comorbidity of personality disorder (PD) and attention deficit/hyperactivity disorder (ADHD) has been suggested in several reports. However, assessment of PD is problematic, and studies have over relied on baseline evaluations.
METHODS: Forty-seven patients entered a double-blind trial of osmotic release oral system (OROS) methylphenidate (MPH). Patients were assessed at baseline with the Wisconsin Personality Inventory IV (WISPIIV) and the Structured Clinical Interview for DSM-IV Axis II Personality Disorders (SCID-II). Following the study, all information—including tests, family reports, and extended clinical observations—produced a final PD diagnosis. Three post hoc categories were created: PD-negative (no PD), PD-positive (1 PD), and PD-plus (2 or more PDs).
RESULTS: Twenty-one (45%) patients had a PD on the final assessment vs 62% using SCID-II and 33% using WISPI-IV; final PD diagnosis revealed 9% cluster A, 17% cluster B, and 28% cluster C. Twenty-one percent of patients experienced multiple disorders. Using a weighted kappa, the number of PDs on the final assessment correlated with the WISPI-IV (κ =.53; P > .001) and the SCID-II (κ =.70; P < .001). However the SCID-II overidentified and the WISPI-IV underidentified PD.
CONCLUSION: Almost all PDs were represented in this sample, and past emphasis on cluster B appears unwarranted. Although the SCID-II and WISPI-IV had limited success in identifying specific PDs, they were more successful in identifying the number of PDs present in each patient. The small sample makes these findings preliminary.