Exercise for Cognitive Symptoms in Depression: A Systematic Review of Interventional Studies

Objective: To explore the effect of exercise on cognition in depression as well as the impact of potential moderators and intervention type. Method: Controlled and uncontrolled interventional studies that described an exercise intervention and cognitive outcomes in participants with major depressive disorder (MDD) were included following a search of Pubmed, Ovid Medline, PsycInfo and Embase from inception to January 2017. Meta-analyses were conducted to calculate Hedges' g using a random-effects model. Meta-regression explored the relationships among age, baseline cognition, frequency and duration of exercise, and cognitive outcomes. Subgroup analyses were also conducted according to type and intensity of exercise interventions. Results: Of 12 controlled studies and 3 uncontrolled studies that met inclusion criteria, 9 (642 patients) were included in the meta-analysis. No significant effect of exercise was found on global cognition (Hedges' g = 0.08, P = 0.33, I-2 = 0%) or on individual cognitive domains. Meta-regression analyses failed to find significant relationships among participant age, baseline cognition, number of exercise sessions per wk, duration of exercise per wk, total duration of exercise during the intervention, or improvement in global cognition. Interventions combining physical with cognitive activity significantly improved global cognition (P = 0.048), whereas low-intensity interventions were also positive (P = 0.048). Conclusions: No impact of physical exercise was found on cognition in MDD overall. However, we found that interventions combining physical and cognitive activities had a positive impact, and that lower-intensity interventions, where adherence was improved, also impacted positively. There remains a lack of high-quality data in this population.