Supplementary Material for: Adherence to Physical Activity Interventions in Major Depressive Disorder: A Systematic Review and Meta-Analysis

Introduction: Non-adherence is a barrier to the effectiveness of physical activity (PA) interventions for major depressive disorder (MDD). This systematic review and meta-analysis identified reported adherence-related outcomes, compared adherence rates of PA and non-PA interventions in MDD, and determined predictors of adherence. Methods: MEDLINE, APA PsycINFO, CINAHL Plus, and SPORTDiscus were searched until September 5th, 2024. Pooled estimated risk differences [RDs] and 95% confidence intervals [CIs] were calculated using fixed-effects or random-effects models. Meta-regression explored predictors of adherence. Results: Ninety-seven studies were included in this review, and 91 studies in the meta-analysis. Adherence-related outcomes for analyses included rates of intervention receipt, retention, protocol adherence, and session attendance. Retention was the most commonly reported outcome, with no significant difference between PA and non-PA interventions. Similarly, there were no significant differences in intervention receipt and session attendance. However, PA interventions had significantly lower protocol adherence than non-PA interventions (RD = –0.15; 95% CI: –0.23, –0.08). Severe baseline depressive symptoms, longer intervention durations, and in-person delivery predicted retention rates. Longer PA sessions predicted intervention receipt and supervision of activities predicted attendance rates. Conclusion: Participants with MDD demonstrate lower protocol adherence to PA interventions than to interventions without a PA component. This result was based on a paucity of studies. Rates of intervention receipt, retention, and attendance were comparable in PA and non-PA interventions. Studies could benefit from including individuals with greater depressive symptom severity and supervised activity. With replication, findings could improve the design of, and increase adherence to, PA interventions in MDD.