Supplementary materials to: Efficacy of psychological treatments for patients with schizophrenia and relevant negative symptoms: A meta-analysis

Background: Recent meta-analyses on the efficacy of psychological treatments for the negative symptoms of schizophrenia included mostly trials that had not specifically targeted negative symptoms. To gauge the efficacy of such treatments in the target patient population – namely people with schizophrenia who experience negative symptoms – we conducted a meta-analysis of controlled trials that had established an inclusion criterion for relevant negative symptom severity. Method: We conducted a systematic literature search and calculated random-effects meta-analyses for controlled post-treatment effects and for pre-post changes within treatment arms. Separate analyses were conducted for different therapeutic approaches. Our primary outcome was reduction in negative symptoms; secondary outcomes were amotivation, reduced expression, and functioning. Results: Twelve studies matched our inclusion criteria, testing Cognitive Behavioral Therapy (CBT) vs. treatment-as-usual (k = 6), Cognitive Remediation (CR) vs. treatment-as-usual (k = 2), CBT vs. CR (k = 2), and Body-oriented Psychotherapy (BPT) vs. supportive group counseling and vs. Pilates (k = 1 each). Accordingly, meta-analyses were performed for CBT vs. treatment-as-usual, CR vs. treatment-as-usual, and CBT vs. CR. CBT and CR both outperformed treatment-as-usual in reducing negative symptoms (CBT: Hedges’ g = -0.46; CR: g = -0.59). There was no difference between CBT and CR (g = 0.12). Significant pre-post changes were found for CBT, CR, and to a lesser extent for treatment-as-usual, but not for BPT. Conclusion: Although effects for some approaches are promising, more high-quality trials testing psychological treatments for negative symptoms in their target population are needed to place treatment recommendations on a sufficiently firm foundation.