To provide an update of outcome studies of schema group therapy for personality disorders and the effect of comorbidity in order to explore whether schema group therapy might be effective for this patient group and what dosage is required.

Studies of short-term schema group therapy for personality disorders with or without comorbidity show moderately effective results but the majority of patients fail to achieve full remission from global psychological symptom distress. Preliminary findings revealed that those unremitted patients might benefit from 40 to 60 sessions. Patients with severe personality disorders (such as borderline personality disorders) seem to need longer and/or more intensive treatment dosage to recover.

We advocate short-term schema therapy in groups as a valuable first step in a stepped-care programme for patients with moderate personality disorders and comorbidity.

Treatment extension or treatment intensification may be indicated in patients who do not recover. Patients with severe personality disorders seem to require long-term outpatient group treatment, with a combination of group and individual treatment being preferable. High-quality randomized controlled trials are needed in order to determine which treatment dosage is necessary for whom.