Diagnostic discriminability of dysthymia and depressive personality disorder

The Depressive Personality Disorder (DPD) is currently being considered for inclusion in future editions of DSM. However, there is little empirical research on DPD as currently defined in DSM-IV, including whether this disorder is sufficiently distinct from Dysthymic Disorder (Dysthymia). The goal of this study was to explore the relationship between DPD and Dysthymia with a sample of depressed outpatients. Scales were developed for the diagnostic criteria for both DPD and Dysthymia. These scales were then analyzed using cluster and factor analysis. Retroactive diagnostic assignment for these two disorders was also made using these scales. It was hypothesized that if DPD is a viable diagnostic category, then the DPD traits and Dysthymia symptoms would fall into different clusters, produce separate factors, and the comorbidity would be small. Two clusters and two factors, each with a close correspondence to DPD and Dysthymia, were statistically extracted from combined symptom and trait scales. However, 95% of those cases identified as meeting diagnostic criteria for DPD also met criteria for Dysthymia. Despite the ability to distinguish statistically DPD traits from Dysthymia symptoms, there was a high degree of comorbidity, compromising the clinical utility of DPD. The results do suggest, however, that DPD might be best conceptualized as a subcategory of Dysthymia.