Physical exercise for negative symptoms of schizophrenia: Systematic review of randomized controlled trials and meta-analysis

Introduction: The negative symptoms of schizophrenia contribute strongly to functional impairment but are inadequately treated by antipsychotic medication. Several studies have suggested that physical exercise could reduce the negative symptoms. Methods: We conducted a systematic review and a meta-analysis of randomized controlled trials (RCTs) examining the effectiveness of physical exercise interventions in improving the negative symptoms of schizophrenia using different databases and trial registries. Results: Seventeen RCTs were included in the meta-analysis (n = 954 patients). Overall, the results revealed a significant beneficial effect of physical exercise on negative symptoms. We conducted a subgroup analysis differentiating between aerobic interventions (12 RCTs) and non-aerobic interventions (5 RCTs). Aerobic exercise reduced negative and positive symptoms, while this was not the case for non-aerobic interventions. A sensitivity analysis including only studies with a low risk of bias confirmed the effect on negative but not on positive symptoms. Conclusion: Aerobic exercise had a beneficial effect on negative symptoms, albeit with a small effect size. The conclusions are limited by the fact that the included studies did not assess patients for predominant or primary negative symptoms. Given the important role of exercise for physical health, the additional effects on negative symptoms are promising and justify further research to disentangle the effects on primary and secondary negative symptoms.