Background: Exercise is considered as a complementary and alternative medicine (CAM) treatment for depression1 but the effectiveness of exercise for several mental illnesses is still debated2. Purpose: The aim of this systematic review was to evaluate meta-analyses that  investigated the effects of physical exercise as an additional treatment for people living with mental illnesses.
Methods: This systematic review was conducted in PubMed, Cochrane Library, Web of Science and PsycINFO databases, until June 2019. We searched for meta-analyses of clinical trials that investigated the effects of physical exercise in the treatment of mental illness. Only meta-analyses investigating the effect of any type of physical exercise as a treatment for patients with clinical diagnosis were included. Effects sizes were interpreted according Cohen (1988) as: small > 0.2, moderate > 0.5 or large > 0.8. Results: A total of 37 meta-analyses were included: Dementia/MCI (n = 12), Depression (n = 10), Schizophrenia (n = 4), Eating Disorder (n = 2), Substance Use Disorder (n = 2), Anxiety Disorder (n = 2), Attention Deficit Hyperactivity Disorder (n = 2), Autism Spectrum Disorder (n = 1), ASD/ADHD (n = 1), Post traumatic Stress Disorder (n = 1). The higher and lower effects size for main clinical symptoms were: in SUD for illicit drugs abstinence rates (SMD = 4.13) and alcohol comsumption AUDIT Score (SMD = 0.37); Depressive Symptoms in older adults (SMD = 1.88) and adults (SMD = 0.57); Dementia for Global Cognition (SMD = 1.12) and (SMD = 0.30). For Schizophrenia, the same study showed an ES of Total Psychiatric Symptoms (SMD = 0.16) and (SMD = 0.72), after performing a sensitivity analysis to exclude trials of low intensity exercises control groups for yoga interventions. In general, the lower ES found was for Anxiety Disorder (SMD = 0.02), however, the most recent meta-analyses that excluded active control groups found a moderate EF (SMD = 0.58). No meta-analysis verified a negative effect of these interventions in clinical outcomes. Conclusion: Although the great variability of effect sizes and methodological problems verified in some studies, exercise improves general symptoms for several mental illness and should be recommended as a CAM treatment for people with mental illness. 
References: 1. Ravindran AV, et al. Canadian Network for Mood and Anxiety Treatments (CANMAT) 2016 Clinical Guidelines for the Management of Adults with Major Depressive Disorder: Section 5. Complementary and Alternative Medicine Treatments. Can J Psychiatry. 2016 Sep;61(9):576–87. 2. Stubbs B, et al. EPA guidance on physical activity as a treatment for severe mental illness: a meta-review of the evidence and Position Statement from the European Psychiatric Association (EPA), supported by the International Organization of Physical Therapists in Mental Health (IOPTMH). European Psychiatry. 2018 Oct;54:124–44.  
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EXERCISE AS TREATMENT FOR PEOPLE WITH MENTAL ILLNESS: A SYSTEMATIC REVIEW OF META-ANALYSES