Validity of PDQ4+ self-screening to assess the impact of personality disorder traits on the course of bipolar disorder

Background: Patients with bipolar disorder (BD) and comorbid personality disorder (PD) have a less favorable illness course than those without comorbidity. They are more difficult to stabilize and make more use of mental health care. This may also be true for PD traits that do not meet criteria for a specific PD. The aim of this study is to investigate whether a simple self-screening instrument (PDQ-4+) can provide an indication of expected severity and course of BD. Methods: Patients completed the PDQ-4+ and the treating clinician independently assessed retrospectively over the past 12 months the course of BD (number of depressive and (hypo)manic episodes, number and duration of hospitalizations, and suicide attempts) and the overall severity of illness using the Clinical Global Impression scale for BP (CGI-BP). Mann-Whitney U tests were used for group comparisons. Spearman rho was used to evaluate associations between the prevalence of PD traits and course of BD. Results: The prevalence of a positive PD screening in the sample with BD was 57.5 %. Patients who screened positive on specific PD were on average rated as more severely ill. More importantly, the total number of all dysfunctional personality traits was associated with less favorable course of BD and had a higher validity than any individual PDs. A limitation of our study is the small sample size and retrospective assessment of BD course. Conclusion: Screening with PDQ-4+ helps to identify a group at risk for a more severe illness course of BD. More important than meeting formal criteria for any PD are the accumulation of dysfunctional personality traits in patients with BD.