Physical Activity and Depression and Anxiety Disorders: A Systematic Review of Reviews and Assessment of Causality

Introduction: Depressive and anxiety disorders are leading contributors to global mental ill health. Physical activity (PA) reduces symptoms of depression and anxiety and may lower incidence. This review of reviews provides an overview of epidemiologic evidence on the strength of association between PA and incident depression and anxiety and assesses causality. Methods: Systematic searches were conducted in Embase and PubMed for reviews (January 1, 2000–March 19, 2020), updated to October 15, 2022. Two reviewers independently assessed methodological quality using AMSTAR. Evidence was synthesized narratively, and Bradford Hill criteria were applied to assess causality. Results: Of 770 records, 4 reviews met inclusion. Two were high quality and two low quality. Pooled estimates from included reviews indicated high PA was associated with reduced risk of incident depression (adjusted RR=0.83, 95% CI=0.76, 0.90) and reduced odds of incident anxiety (adjusted OR=0.74, 95% CI=0.62, 0.88) compared with low PA. PA was assessed as probably causally related to both depression and anxiety. Discussion: Evidence derives from systematic reviews of observational data; further high-quality studies, including randomized controlled trials, would strengthen the evidence base. Findings support considering PA in prevention strategies for mental ill health.