Estimating the prevalence of borderline personality disorder in psychiatric outpatients using a two-phase procedure

The prevalence of borderline personality disorder (BPD) in outpatient clinics varies greatly (7%-27%) depending on the setting and methodology. We examined the cross-sectional rate of BPD in a general adult outpatient university clinic using a 2-phase procedure: (1) we screened all registered patients with the self-report SCID-II-PQ and (2) we administered the Revised Diagnostic Interview for Borderlines (DIB-R). Sixty-six percent (239/360) of the clinic patients completed the screening: About 72.4% (173/239) (95% confidence interval [CI] = 66.7%, 78.1%) were positive for BPD on the Structured Clinical Interview for DSM-IV Personality Disorders-Patient Questionnaire (SCID-II-PQ), and 22.6% (54/239) (95% CI = 17.3%, 27.9%) were positive for BPD on the DIB-R. Our BPD rate was somewhat higher than recent semistructured interview studies (9%-18%). We believe this is due, in part, to our cross-sectional design and our decision not to exclude acute Axis I disorders. Mostly, however, we believe that our 22.6% incidence of BPD arises from the high morbidity of our sample. Demographic data from 130 of 131 DIB-R completers reveal the following: mean age was 40.2 years, 75.4% were female, most patients were unable to work, and they averaged 3.8 lifetime hospitalizations.