Supplementary Material for: Are Group Psychotherapeutic Treatments Effective for Patients with Schizophrenia? A Systematic Review and Meta-Analysis

<b><i>Background:</i></b> Different psychotherapeutic treatments for schizophrenia are delivered in groups. However, little is known about the effectiveness of these group therapies for people with schizophrenia across different treatments with varying therapeutic orientations. This review aimed to (1) estimate the effect of different group psychotherapeutic treatments for schizophrenia and (2) explore whether any overall ‘group effect' is moderated by treatment intensity, diagnostic homogeneity and therapeutic orientation. <b><i>Methods:</i></b> A systematic search of randomised controlled trials exploring the effectiveness of group psychotherapeutic treatments for people with schizophrenia was conducted. Random-effect meta-analyses on endpoint symptom scores compared group psychotherapeutic treatments with treatment as usual and active sham groups. Findings on social functioning were described narratively, and meta-regression analyses on group characteristics were carried out. <b><i>Results:</i></b> Thirty-four eligible trials were included. A weak-to-moderate significant between-group difference in favour of group psychotherapeutic treatments was found for negative symptom scores (standard mean difference = -0.37, 95% confidence interval -0.60, -0.14; p &lt; 0.01, I² = 59.8%) only when compared to treatment as usual and not to active sham groups. Improved social functioning was reported as a treatment outcome in the majority of studies compared to treatment as usual. The ‘group effect' on negative symptoms was positively related to ‘treatment intensity' (β = 0.32, standard error = 0.121; p &lt; 0.05). <b><i>Conclusion:</i></b> Group psychotherapeutic treatments can improve negative symptoms and social functioning deficits in the treatment of schizophrenia. The effect occurs across different treatments and appears to be non-specific. Future research should identify the underlying mechanisms for the positive effect of participating in groups and explore how they can be maximised to increase the therapeutic benefit.