Walking the Black Dog: A systematic review and meta-analysis on the effect of walking interventions on depressive symptom severity

Background and aims: Depression is a frequent and debilitating mental illness. The plethora of common practical and psychological barriers to evidence-based care warrant more easily accessible interventions, such as behavioral activation. Walking represents an easy-to-prescribe, highly practicable, and flexible form of behavioral activation. We conducted a systematic review and meta-analysis to assess the effects of walking interventions on depressive symptom severity. Methods: Scopus, PubMed, Web of Science, MEDLINE, APA PsycArticles, and APA PsycInfo were searched to identify German- and English-language randomized-controlled trials involving adults (age ≥18 years), that compared a walking intervention with a control group and employed self-report measures of depressive symptom severity in a pre-post design. Results: Our literature search yielded k = 10,898 records, k = 27 of which were included in the systematic review (n = 1,578, 74.2% female). Study characteristics varied substantially, with overall risk of bias being moderate to high. For the k = 15 studies included in the meta-analysis, the initial effect of SMD = -.33 in favor of walking vs. control conditions lost significance after excluding outliers and studies with high risk of bias. Of all examined moderator variables (e.g., control group type, sample type, intervention delivery frequency, age, percentage of female participants), only baseline depressive symptom status meeting clinical criteria cut-offs emerged as significant. Conclusion: While the heterogeneity in intervention designs and flexible adaptability are clear strengths of walking interventions, rigorous empirical evidence for their beneficial effects on subthreshold and clinically relevant depression remains sparse, providing future research endeavors clear imperatives.