Effectiveness of different modalities of psychotherapeutic treatment for patients with cluster C personality disorders: results of a large prospective multicentre study.

Background: No previous studies have compared the effectiveness of different modalities of psychotherapeutic treatment, as defined by different settings and durations, for patients with cluster C personality disorders. The aim of this multicentre study was to compare the effectiveness of 5 treatment modalities for patients with cluster C personality disorders in terms of psychiatric symptoms, psychosocial functioning, and quality of life. The following treatment modalities were compared: long-term outpatient (more than 6 months), short-term day hospital (up to 6 months), long-term day hospital, short-term inpatient, and long-term inpatient psychotherapy. Methods: The study was conducted between March 2003 and June 2008 in 6 mental health care centres in the Netherlands, with a sample of 371 patients with a DSM-IV-TR axis-II cluster C diagnosis. Patients were assigned to 5 different modalities of psychotherapeutic treatment, and effectiveness was assessed at 12 months after baseline. An intention-to-treat analysis was conducted for psychiatric symptoms (Brief Symptom Inventory), psychosocial functioning (Outcome Questionnaire-45), and quality of life (EQ-5D), using multilevel statistical modelling. As the study was non-randomised, the propensity score method was used to control for initial differences. Results: Patients in all treatment groups had improved on all outcomes 12 months after baseline. Patients receiving short-term inpatient treatment showed more improvement than patients receiving other treatment modalities. Conclusions: Psychotherapeutic treatment, especially in the short-term inpatient modality, is an effective treatment for patients with cluster C personality disorders.