Longitudinal comparison of depressive personality disorder and dysthymic disorder.

BACKGROUND Few studies have compared the related diagnostic constructs of depressive personality disorder (DPD) and dysthymic disorder (DD). The authors attempted to replicate findings of Klein and Shih in longitudinally followed patients with personality disorder or major depressive disorder (MDD) in the Collaborative Longitudinal Personality Disorders Study. METHODS Subjects (N = 665) were evaluated at baseline and over 2 years (n = 546) by reliably trained clinical interviewers using semistructured interviews and self-report personality questionnaires. RESULTS Only 44 subjects (24.6% of 179 DPD and 49.4% of 89 early-onset dysthymic subjects) met criteria for both disorders at baseline. Depressive personality disorder was associated with increased comorbidity of some axis I anxiety disorders and other axis II diagnoses, particularly avoidant (71.5%) and borderline (55.9%) personality disorders. Depressive personality disorder was associated with low positive and high negative affectivity on dimensional measures of temperament. Depressive personality disorder subjects had lower likelihood of remission of baseline MDD at 2-year follow-up, whereas DD subjects did not. The DPD diagnosis appeared unstable over 2 years of follow-up, as only 31% (n = 47) of 154 subjects who had DPD at baseline and also had follow-up assessment met criteria on blind retesting. LIMITATIONS Results from this sample may not generalize to other populations. CONCLUSIONS Depressive personality disorder and dysthymic disorder appear to be related but differ in diagnostic constructs. Its moderating effect on MDD and predicted relationship to measures of temperament support the validity of DPD, but its diagnostic instability raises questions about its course, utility, and measurement.