Objective To analyse the effectiveness of mentalization-oriented outpatient group therapy following 5-month day hospital treatment.

Methods Twenty-two patients with personality disorders participated. All were consecutively referred and diagnosed according to standardized criteria and had completed a 5-month long psychotherapeutic day hospital treatment. Intervention consisted of once a week mentalization-oriented group therapy for up to 3 years. Outcome on acute symptoms included hospitalizations and suicide attempts, the more enduring social and interpersonal problems were assessed by standardized questionnaires regarding symptoms, interpersonal problems, social functioning and vocational status. Outcome measures were analysed within the framework of generalized estimating equations at the beginning and at the end of treatment, and at 2 years follow-up.

Results Average treatment length was 2 years. There was no dropout from treatment. Significant improvements were observed on the Symptom Checklist SCL-90-R, Personality Severity Index Score, Inventory of Interpersonal Problems-Circumplex version, Clark's Personal and Social Adjustment Scale, Global Assessment of Functioning, hospitalizations and vocational status. At follow-up, these results further improved significantly.

Conclusion Long-term mentalization-oriented outpatient group therapy was associated with a reduction in both acute symptoms and the more long-lasting social and interpersonal problems in this patient group. At follow-up, results further improved, were paralleled by a level of hospitalizations which dropped to almost none, a marked decrease in the use of psychological treatment, and a clearly improved vocational status. Copyright © 2010 John Wiley & Sons, Ltd.