Association of comorbid personality disorders with clinical characteristics and outcome in a randomized controlled trial comparing two psychotherapies for early-onset persistent depressive disorder

Background: Persistent depressive disorder (PDD) is associated with high rates of comorbid personality disorders (PD). The association of comorbid PD and clinical characteristics has not been systematically studied in PDD. Results regarding effects on treatment outcome are heterogeneous. Methods: We analyzed the association of comorbid personality disorders with clinical characteristics and outcome in a randomized controlled trial comparing the disorder-specific Cognitive Behavioral Analysis System of Psychotherapy (CBASP) with nonspecific supportive psychotherapy (SP) in patients with early-onset PDD. The main outcome measure was the Hamilton Rating Scale for Depression (HRSD-24). Further baseline measures were comorbid axis-I diagnoses (SCID-I), quality of life (QLDS), global functioning (GAF), interpersonal problems (IIP-64) and childhood maltreatment (CTQ). Results: Out of the 268 patients, 103 (38.4%) met criteria for at least one PD. PD was associated with higher rates of axis I comorbidities (mainly anxiety disorders) and interpersonal problems (patients with PD were more vindictive, more self-sacrificing, less assertive and more inhibited socially than patients without PD). There was no significant main effect of PD on treatment outcome and no significant interaction between PD and treatment group. Limitations: The main limitation was the exclusion of patients with certain personality disorders (antisocial, schizotypal, and borderline personality disorders). Furthermore, the study was underpowered to find interaction effects of small size. Conclusion: Persistently depressed patients with and without comorbid PD primarily seemed to differ in the rate of axis I comorbidity and the severity of interpersonal problems. Treatment outcomes appear to be not significantly affected by the presence of PD.